Thursday, December 28, 2006

The Mouse is dreaming that it is in a Trap!!

New research has established that mice dream and during their sleep there is a two-way dialog between the hippocampal recent day memory area and the neo-cortex that is believed to be involved in long-term memory.


The content of the mice dream is also no longer secret. In the sleep they are replaying the sequence of steps that they had executed in a maze, but in a reverse order, and in lesser time and in general are rehearsing the structure of the maze (the mouse trap). Learning, it is to be remembered, arises from these replays of fast rewinds and sleep it seems is necessary for learning.

Some quotes from the article:


During nondreaming sleep, the neurons of both the hippocampus and the neocortex replayed memories — in repeated simultaneous bursts of electrical activity — of a task the rat learned the previous day.

Earlier this year Dr. Wilson reported that after running a maze, rats would replay their route during idle moments, as if to consolidate the memory, although the replay, surprisingly, was in reverse order of travel. These fast rewinds lasted a small fraction of the actual time spent on the journey.
In the findings reported today, the M.I.T. researchers say they detected the same replays occurring in the neocortex as well as in the hippocampus as the rats slept.

The rewinds appeared as components of repeated cycles of neural activity, each of which lasted just under a second. Because the cycles in the hippocampus and neocortex were synchronized, they seemed to be part of a dialogue between the two regions.

Because the fast rewinds in the neocortex tended to occur fractionally sooner than their counterparts in the hippocampus, the dialogue is probably being initiated by the neocortex, and reflects a querying of the hippocampus’s raw memory data, Dr. Wilson said.

“The neocortex is essentially asking the hippocampus to replay events that contain a certain image, place or sound,” he said. “The neocortex is trying to make sense of what is going on in the hippocampus and to build models of the world, to understand how and why things happen.”


PS: My blog post has deliberately used words like 'dream', 'mouse' and 'traps' instead of the correct 'sleep', 'rats' and 'mazes': just to come up with a juicy headline!!


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Neurogeneisis, learning and small-world networks

Continuing this blog's recent focus on categorization, one possibility of how new items are classified has been hypothesized as either assimilitaion (adding the item to an existing schema in the feature space) or accomodation (addition of a new schema around the item in the feature space). We'll leave aside the newly introduced concept of Restructuring for this particular discussion.

Schemata, it is to be remembered, are conceptualized as nothing but a named cluster in the feature space. If we become a bit more audacious, we can posit that the clustering in the feature space is mimicked by the actual clustering/ connectivity of neurons in the Hippocampus (or the appropriate semantic memory brain module), with each neuron representing a particular item- say a neuron being a Halley Barry neuron. These neurons would not be randomly distributed- they form a small-world model with local clustering and bistability. whenever a group of neurons get activated together (and also belong to a cluster or clique), we can say that the memory of that category is activated.

Further suppose that learning and memory are crucially dependent on Neurogeneisis and new learning (of concepts ) happens by insertion of a new node (neuron in the small-world network of brain) and connecting it appropriately with other neurons.

As an example consider that all face recognition cells cluster together in the brain and the concept of face is activated by simultaneous activation of all cells of this cluster. The fact that a new visual stimulus (a novel human face of a stranger) is a face is determined by calculating the stimulus features and their difference from the prototypical/ exemplar face neurons and their features. A match so determined not only enables us to say that this new stimulus is a face (as this input would activate the face clique) , but would also give us an idea of where to place a new neuron that may encode for this new face and how to connect this with other neurons and with which other neurons.

Now whenever we encounter a novel stimulus we have two possibilities. If it matches some existing cluster / category, we encode this new memory by placing a new neuron coding for this in the region of that category in the feature space and (crucially) following preferential attachment attach it in a manner such that the probability of its linking to any other neighboring neuron is in proportion of the links that old neuron already has. (This can be readily implemented in brains as axonal connections will whither if not much functional activity happens at the synapse formed between the new neuron and the older one) . This is akin to assimilation of a new memory/ learning neuron. this method of insertion still keeps the neural net a small-world network.

Now consider the second case when the novel stimuli matches no older categories but necessitates that we form a new category if we have to represent that new item in the feature space. We need accommodation here. On the neural level this is still accomplished by inserting a new neuron, but this time the new node is not peripheral- the new neuron is a hub (category) neuron. So we use the method of copy to insert the new element. We copy the links (partially) of a neighboring hub (cluster center/ category label neuron) and use that link structure to link the newly introduced neuron in the small-world network. the network still remains scale-free and we have introduced a hub or a new category in this case.

All this seems very exciting. Some snippets from wikipedia article on scale -free networks are very relevant.


The mostly widely known generative model for a subset of scale-free networks is Barabási and Albert's (1999) rich get richer generative model in which each new Web page creates links to existent Web pages with a probability distribution which is not uniform, but proportional to the current in-degree of Web pages.

A different generative model is the copy model studied by Kumar et al. (2000), in which new nodes choose an existent node at random and copy a fraction of the links of the existent node. This also generates a power law.

Recently, Manev and Manev (Med. Hypotheses, 2005) proposed that small world networks may be operative in adult brain neurogenesis. Adult neurogenesis has been observed in mammalian brains, including those of humans, but a question remains: how do new neurons become functional in the adult brain? It is proposed that the random addition of only a few new neurons functions as a maintenance system for the brain's "small-world" networks. Randomly added to an orderly network, new links enhance signal propagation speed and synchronizability. Newly generated neurons are ideally suited to become such links: they are immature, form more new connections compared to mature ones, and their number but not their precise location may be maintained by continuous proliferation and dying off.
I am excited, what about you?

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Markers for Psychosis and Mania

A recent review of the COMT genotype Met/VAL SNP on psychiatric phenotypes of schizophrenia, bipolar mood disorder and schizoaffective disorder seems to suggest that the SNP's effcet mya be more of modifying the symptoms (with Val conferring positive symptom susceptibility and MET negative symptom susceptibility) of psychosis and mania, rather than conferring susceptibility to the diseases per se. Also the association, in European populations primarily, would be between both psychosis and mania (schizoaffcetive) present rather than juts a simple diagnosis of schizophrenia or bipolarity.

The narrowing of COMT linkages to the combination of Mania and Psychosis loks like a step forward and the distinction between symptom modifying effects and the distinction between symptoms based on their being positive (additions of functionality) or negative (deletion of functionality) seems to be a step in the right direction.

This differential effect of having a Met or Val allele on symptom type (positive and negative) is also inline with the inverted U model of dopamine levels that suggests that there is a range of dopamine levels that is good for the body(brain) and beyond either end there are deleterious effects. It could be that while a Met allele confers protective advantage for positive symptoms, it is an aggravator for negative symptoms. Depending on dopamine environmental levels, the person having Met allele may or may not show the symptoms of mania/ scizophrenia.

I am also intrigued by the BDNF met/val allele effect on anxiety susceptibility and forced to think whether there too the effect may be that of symptom modification rather than susceptibility?

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Wednesday, December 27, 2006

Categorization, Memory, small-world networks and neural architecture

In the last post I had wondered about the clustering based solution to categorization and how they may also inform us about how memory (semantic variety) is stored in brain, as semantic memory is best modeled by an associational or confectionist network.

Thus, a semantic memory based on clustering models may consist of associations between clusters or categories of information. For example one cluster may correspond to the names of countries and another to name of cities. A particular type of connection or association between these two clusters may map a relation of ----IS A CAPITAL OF ---- type where for example the fact that Paris is the capital of France is stored. For this knowledge to exist, one has to have prior notions of France is a Country and Paris is a City and on top of that an associational relation between the individual entities France and Paris belonging to particular clusters.

Much of this would be more apparent once relational models of categorization are also covered. For now let us assume that (semantic) memory itself may consist of clusters of neurons that are also interconnected. Interestingly one such neural architecture, that has also been able to simulate short-term memory has been the small-world network model. In this a large number of nodes (neurons ) are connected by edges (synapses) as in a typical random graph. These small-world networks are special in the sense that they have high clustering coefficients and low mean path length. Translated in English, this means they exhibit more than chance clustering (to enhance local processing) as well as display a small value of smallest mean path length (reflecting ease of global processing).


It is intriguing thta in the short term memory model using small-world networks simulation, the researchers found that the model could exhibit bistability, which may be crucial for memory formation. In bistability, the cluster or functional region corresponding to a particular memory can be in two states, depending on an input variable. Thus, a pulse (direction of attention) can activate/ deactivate a memory.

Crucially, it can be hypothesized that as the small-world network model of memory/ categorization is good for local-global processing as well as reflective of the actual brain and AI simulation architectures, the entire brain is a small-world network adequately categorizing and representing the sensory, motor and cognitive information and processing them.


A recent MEG based study has established the fact that the small-world network topology exists in functional sphere in the brain at all oscillatory levels (crucial for binding) and that seems very promising.

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Tuesday, December 26, 2006

Categoristation: how to bookmark the interesting pages on the web!

In an earlier post, I had touched upon the different categorization theories that are in prevalence. One of these that was discussed in details was the prototype Vs exemplar method that was based on clustering and involved different representational methods of the categories thus derived.

This post is about how a new item is allocated to a pre-existing category. Simplistically, and in the last post this was the position I had taken, it seems apparent that by calculating the distance of a new item in feature space from the central tendencies of the neighboring clusters (the prototypes/ exemplars) one can find a best fit with one of the clusters and allocate the new item to that category.

This is simplistic as it explains fitting of new items to existing categories, but does not include any mechanisms for formation of new categories.

The analogical approach I take here is of how do I decide in which folder to add a new bookmark of an interesting page found on the web. Most probably the names I have chose for my bookmarks folders are reflective of the central tendencies (common prominent features) of all pages bookmarked in that folder. I would normally look at the new page, and also at my existing folders and see if there is a best fit. If so I juts file the new bookmark under the best-fit existing folder. Slightly extending the concept of categorization to resemble that of a schema, this is the classical case of assimilation in a schema.

However, in case the new web-page cannot be filed under any existing bookmark folder, I would usually create a new folder (with an adequate descriptive name based on the location of the web page in the feature space) and file the new bookmark under that new folder. This is akin to trying to fit in a novel item into existing clusters in the feature space, only to discover, it doesnt fit well with any cluster, but is an outlier. The best way to accommodate such an outlier , in my opinion, is to create a new cluster around the outlier. Extending this to schema, it is not hard to see that this is the classical case of accommodation and formation of a new schemata to incorporate a novel item that cannot be assimilated in existing schema.

Piaget, of course , stopped here (and so do I, sometimes, when managing my bookmarks!). but I would like to venture firth and discuss the other process that I engage in , very infrequently, to keep my bookmarks in good shape. This is what I would call reorganization or restructuring. when I restructure my bookmarks, I change the names, I move bookmarks form one folder to another , I merge bookmarks and also at times create more than a few sub folders. Also, interestingly, I delete some of the old bookmarks; while am captivated by some of the bookmarks and even forget to complete the restructuring part.

I believe that we too indulge in restructuring of our Schema/ categories periodically (it may be as frequent as daily during REM sleep) and that a crucial form of learning is not juts Assimilation and Accommodation, but also Restructuring. Also it is my contention, that we consciously remember anything only because we have actively restructured that information and embedded it in a contextual narrative. In the absence of restructuring, there can be information that can be used, but no conscious knowledge.

I plan to tie this up with the 3 factor model of memory that is emerging. One factor of the memory system uses familiarity detection (assimilation), the other novelty detection(accommodation), while the other involves conscious and contextual recollection(restructuring).

I also propose that these three factors are behind the three kinds of memory (content-wise and not duration wise). The first type of memory is semantic (or noetic)- facts like France's capital is Paris; the second is procedural (or anoetic) - learning how to drive- and is unconscious; while the third is episodic or autonoetic) - personally remembered events and feelings) . Of course memories would also differer along the time dimension- working memory, long-term memory etc. , but that discussion is for another day.

Also a brief not to myself - how this may be linked with Hughling-Jackson's theory of 3 states of consciousness and how they are differentially affected in dissociation- the autonoetic memory would be affected first- the noetic second and the anoetic or unconscious memory last in dissociation.

Returning back to categorization, this approach of adding new items either by assimilation, accommodation or restructuring is more guided my Mind-Is-A-Container metaphor. Other metaphors of mind- assuming it theory like - may yield to new and interesting views of how we form a theory-like theory of categorization. The other minor variation to above mind is a container metaphor may be using labels for bookmarks (instead of folders)- this is what Google bookmarks and del.icio are using. I haven't experimented with that approach to bookmarking extensively, so am not sure what new insights can be gained form them. For those readers, who use labels to organize bookmarks, their insights as comments, would be greatly appreciated.

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Wednesday, December 20, 2006

Moral Intuitions: Musings continued.

In the last post, we dwelled on the classical trolley problem as well as a new type of moral dilemma that may be termed as the Airplane dilemma.

In some versions of the Airplane (as well as the Trolley ) problem, the problem is framed so as to implore us into examining our notions of trusting or being suspicious of strangers (terrorists scenarios) and to take into account the past as well as future characteristics of these people (like high IQ and national celebrity status) to arrive at a moral decision, as to serving whom would be a more moral action for the doctor. The airplane problem mostly focuses on Trust Vs Suspiciousness dimension, is people-centered and focuses on assessing people and situations correctly in a limited amount of time. After the decision is made, then the action is more or less straight-forward.

The trolley problem is also similar, but of a somewhat different nature. Here, the focus is on actions and outcomes. The Morality of action is judged by its outcome as well as other factors like whether the (in) action was due to negligence, indirect, personalty motivated etc. The people centered focus is limited to using-as-means versus ends-in-themselves distinction and in the later problems (president-in-the-yard) that of guilty vs innocent. The innocent, careful child playing on unused track, while the careless , ignorant five idiots playing on the used track is another variation that plays on this careful action versus careless action distinction.

It is my contention that while the Trolley problem aptly makes clear the various distinction and subtleties involved in an Action predicate, viz whether the action is intentional, whether it is accidental- and if so how much negligence is involved; whether (in)action could be prevented/ executed differently for different outcomes etc; it does not offer much insight on how to evaluate Outcome Predicate or the Intention Predicates.

In the Trolley Problem, while the intentional vs accidental difference may guide our intuition regarding good and evil , in case of positive or negative outcomes; the careful versus careless (negligent) action guides our intuitions regarding the normal day-to-day good and bad acts. Here a distinction must be made between Evil (intentionally bad outcome) versus Bad acts(accidental or negligent bad outcome).One can even make a distinction between Good acts (performed with good intentions) versus Lucky acts (accidental good outcomes, maybe due to fortuitous care exhibited). Thus, a child playing on an unused track may juts be a 'bad' child; but five guilty men tied on tracks (even by a mad philosopher) are an 'evil' lot. Our intuitions, thus , would be different in the two cases and would not necessarily be determined by utilitarian concerns like number of lives.

Some formulations of the airplane problem, on the other hand , relate to quick assessment of people and situations and whether to trust or be suspicious. The problem is complicated by the fact that should the doctor invest time in gathering more data/ confirming/rejecting her suspicion versus acting quickly and potentially aggravating the situation/ long-term outcome. These formulations and our intuitive answers may tell us more about the intention predicates we normally use. Whether we intend to be trusting, innocent and trustworthy or suspicious, cautious and careful. If cautious and careful, how much assessment/ fact gathering we must first resort to to arrive at the correct decision, before committing to single-minded and careful action.
Should we juts look at the past for arriving at a decision, or should we also predict the future and take that into account? If we do predict the Outcomes, then the Consequence predicate is long-term or short-term? Is it an optimistic or a worst-case outcome scenario?

There are no easy answers. But neither is the grammar of any language supposed to be easy. Constructing valid and moral sentences as per a universal moral grammar should be an equally developmentally demanding task.

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Friday, December 15, 2006

History in the making - the neurogeneisis discovery

There is an old article by Jonah Lehrer in the Seed magazine regarding the historical process via which the fact of neurogenesis in the humna brain was discovered and established.

One of the findings related to the stress/depression and the-lack-of-neurogenesis linkage and the underlying mechanisms that are involved (including sertonergic triggering of cascade reactions that lead to increase in trophic factors). A corollary finding was that enriched environments also lead to more neurogenesis and can help heal the scars formed due to depression/stress by stimulating neurogenesis in the adult brain. How neurogenesis (in areas like hippocampus and dompaminergic neurons) leads to recovery from depression/ stress is still not clear.

To briefly summarize the findings (though it is highly recommended that you read the original article which is very well written):

  1. Neurogenesis happens in adult brains (rats, primates and even humans).
  2. Stress reduces neurogenesis.
  3. Depression and reduced neurogenesis have been found to co-occur.
  4. Enriched environments lead to increase in neurogeneisis. (in rats, marmoset monkeys)
  5. Sertonin-based antidepressants primarily work by increasing neurogeneisis.

Hence inductively it seems probable that Low IQ is caused by Lower SES. (OK, this may seem like a joke...but do go and read the article and Gould's views on the stress and poverty relationships- and I find her views (and her supporting experimental and observational facts) quite plausible.)

The scientists profiled in the article, at that time, were still wondering (and actively exploring) the exact mechanism between neurogenesis and depression/ stress.

My hypothesis of why depression leads to less nurogenesis in hippocampus would be related to the role of hippocampus in memory and learning and how, for example, repeated exposure to shocks in rats leads the rats to exhibit a phenomenon known as 'learned helplessness'. Once the memory of a shockful and distressing repetitive experience is entrenched in the rat's memory, in the hippocampal region, she may not try to explore the environment that much, to discover and learn what has changed regarding the environment, and whether the stressful conditions and environments are over. This may lead to reduced neurogenesis as the rat's brain resigns itself to fate. This inability-to-learn or 'learning helplessness' (my slightly changed term for the same behavioral description) may lead to a vicious downward cycle leading to depression.

Once the neurogenesis is re-triggered, either due to administration of prozac or other antidepressants, or due to Cognitive behavioral therapy (and it had been found using brain scans that these two approaches seem to converge- one working in a top-down fashion (expecations and beliefs), while the other on a molecular and bottom-down fashion ), then the increased neurogenesis leads to an enhanced ability to learn and adapt and thus overcome the depressive epsiode and get rid of the symptoms. In both cases, the brunt of effort to get out of depression is still borne by the individual who is affected.

The other piece of information that caught my fancy was that of the dopimenergic neurogenesis and the potential cure of parkinson's disease based on targetting this pathway. Whether neurogenisis is limited to hippocampal regions, or also happens in the substatntia nigra/ VTA region (where I guess all the dopaminergic neurons reside) is an important question and my lead to more insight as to which all areas of the brain (or all areas) are susceptible to neurogenesis.

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Wednesday, December 13, 2006

Moral Intuitions (alternate title : Who framed roger rabbit?)

Disclaimer: Haven't seen the movie "Who framed roger rabbit", nor know the storyline- just used the alternate title as it is eye-catching:-))

Classical Moral intuitions research has focused on identifying how we arrive at moral conclusions. The Kohlberg's developmental theory is based around identifying the reasoning process, by which, the children arrive at a moral decision regarding a moral dilemma; or identifying an action that would be ethical in a given situation; or forming a moral judgment regarding a given event-outcome.

Much of the discourse is limited by the few example problems around which these dilemmas are framed. A good example is the famous Trolley problem, in which one has to decide whether it would be worth sacrificing a single person, in lieu of five or six others; and its variations involving whether one is in direct contact with the person and is performing an active action of 'sacrificing' the person by pushing him/her from the footbridge; or is merely a bystander and passively (from a distance) pulling a switch that would direct the trolley to a different track. Variations include whether the person (who if sacrificed could save five or six others) is related to you, or whether he is innocent (a child playing on an unused track) vis-a-vis those being sacrificed are careless and thus not worth saving ( stupid children playing on running tracks).

While some framing of this Trolley problem are in utilitarian terms- one life versus many others, other framings are in emotional & selfish versus sacrificial & rational terms -your child or your action vs other children and universal action (by universal action I mean the same action irrespective of whether you are in touch with the person (the footbridge case) or are merely pulling a lever).

The framing involving 'good/ careful' vs. 'bad/careless' in the good-boy-on-unused-track and bad-boys-on-used-tracks fascinates me the most.

At the outset, let me clarify that in regards to moral dilemmas of this sort, my personal position is reasonably clear. In a discussion some years back with some good friends (not over a cup of coffee; but over an intranet discussion group:-) , while we were discussing this dilemma, I had surmised that while we may debate endlessly what the action should be, the most reasonable guess one can make is that there would be no action at all. In the Trolley switch case, this means that the person my get so much frozen by the decision pressure and inability to arrive at a conclusion, that he/she may not pull the switch at all (the switch that would direct the train/ trolley to the unused track ). Instead, he may just remain frozen- just like one gets frozen sometimes in times of extreme fear- a third reaction apart from the usual fight or flight response. Yet, dilemmas, such as these, and our 'hypothetical' responses to these may somehow tell us more about how we reason about moral situations- whether it is post hoc (just like it is claimed that Consciousness is post hoc)- and if so, why would we be constructing different post-hoc moral reasons for the same dilemma when it is framed in different terms. (Hauser's research shows that the intuitions are different in the classical trolley (switch) versus the personal contact (footbridge) cases.)

Marc Hauser's lab is doing some excellent research in this field and though I have taken their Moral Sense Test, I have a feeling that I have stumbled on a new type of framing and dilemma (that was not present in their tests...though one can never be sure:0) that may enable us to reflect a bit more on our moral reasoning process.

I'll frame it first in neutral terms, and then try to refine it further. Let's call this the Aeroplane problem. Suppose that you are traveling in an Aeroplane, and there is only one doctor present on board, and the Air hostess staff is not sufficiently educated in all first aids. Suppose further that you are way above ground, with any emergency landing at least 20 minutes distant. Suppose, that their are two people on the Airplane, who start getting a third heart attack (they are both carrying medical histories/ badges that tell that it is the third and potentially fatal heart attack (BTW, why is the myth of 3rd heart attack being fatal so enduring?) ), and the heart attacks are almost simultaneous, and only the lone doctor on board can give them the first-aid and resuscitation (CPR) that could ensure that they both remain alive, till the airplane makes an emergency landing (the emergency landing may itself risk the life of all passengers slightly). Now, when all other details are unknown, it is potentially futile to ask which one to attend- you may as well choose one patient and concentrate all efforts on him/her.

Suppose, one of them is an octogenarian, while the other is a teenager. Now, which one should the doctor choose? Suppose one is an old lady, while the other is a young brat, which one should the doctor choose?

Suppose the Doctor has Asthma, and no body else knows how to administer the oral inhalation medicine correctly except for the doctor; then should the doctor take care of a patient or should he/she take care of himself/herself? what if there is only one patient and one doctor? What if there is one doctor and many patients? Would the decision be easy?

Suppose further, that out of the two persons, one is faking heart attack symptoms, while the other is genuinely suffering; should the doctor be able to find out who is who? Would this make the dilemma easier? Would we (the airplane travelers) respect the doctor's decision and let him /her attend to the person s/he thinks is genuinely suffering from heart attack?

Suppose further, that both the patients are terrorists and the doctor says that both are faking symptoms, potentially to hijack the plane; would we listen to the doctor and let him not attend to any of the potential causalities? Or would we try to help ourselves, potentially causing bedlam and fulfilling the plans of the terrorists?

I am sure by now you can conceive of other similar scenarios!! (one that comes to my mind is both the doctor and patient are accomplices and terrorists on-board to cause bedlam and mayhem and hijack the plane. Please let's add as many scenarios in the comments as possible.)

Now let us take a moment to reflect on our moral reasoning process. I believe most of us would be prone to go with our intuitions and would think about rationalizing our decisions later. Thank god, we do have some moral intuitions to guide us in time of indecision/ threat perception.

Suppose that instead of framing the last few scenarios in an anxiety provoking setting (involving terrorists and what-nots), we framed this in terms of forward-looking, futuristic terms.

Suppose that one of the patients is a very promising child (has an IQ of 200/ or is a sport prodigy and is as well-known as Sania Mirza) while the other is again a famous scientist indulging in some ground-breaking research (Say Marie Curie, whose Radioactivity discovery is definitely a very useful discovery); then who should the doctor choose? Should she look at their achievements or potentials? Or should she remain immune to all this and dispassionately ignore all (ir)relevant information? or should s/he be affected by age, gender, race, achievement, potential etc?

Suppose further that instead of well-known celebrities like Abdul Kalam , or Sachin Tendulkar, who are present in the plane, the younger patient is a product of genetic engineering, destined to become a great scientist/ artist/ whatever; while the older patient is working on a top-secret classified dual use research which potentially could help humanity overcome the impending fuel crisis (and related arctic melting, ozone hole etc crisis-she is working on a hydrogen powered (water as fuel) engine, which could be used in automobiles as well as in outer Space like Mars, where only water may be available for refueling). Also, both these persons are not well-known currently and not recognizable by the doctor/ crew/ passengers. Death of the older person would put humanity back by at least 40 years- only after 40 years would someone like the younger patient that the doctor saved (in case the doctor let the older patient die), could have worked out the designs for using water as a fuel again. Now which one should the doctor attend to? Should s/he attend to the young one or the old one? The future or the present?

Should she take the time out to see the credentials (the proof that this child is genetically modified to have a good IQ/ whatever and the proof that this scientist is indeed working on classified research that may potentially help millions) of the patients or should she just act on her intuitions? Why is the reasoning different here as compared to the threat-scenario?

What if the instead of Science frames above, we used frames of Art(I mean artistic frames and not the frames that visual artists use for paintings:-)....Art is much more than visual art:-).

Suppose, that one of them (the older one) could become a Paul Gauguin; while the other (younger one) could become a Van Gogh (again I mean an artist like Gogh and Gauguin, not their works of arts:-) ), now which one should the doctor choose? Why does it become irrelevant as to who should be saved if the frame is of Art, but a question of life-and-death if the frame is of Science?

Finally, some things to note and think about: the Airplane problem is entirely framed in life-saving context (doctor helping save a life); while the Trolley problem is entirely in death-prevention context (someone acting messiah and preventing death of five Vs One; good vs careless etc). Again, Doctors usually give rise to feminine frames with one assuming a doctor to be a female; while the Foreman's are usually entirely male. I hardly believe that framing is all of the problem; or that the framing is done deliberately: the framer of the problems/ dilemmas is equally susceptible to the same framing effects that the readers have experienced-while formulating a problem (a moral dilemma) one may fall prey to the same sorts of Frames that we become susceptible to when thinking about the problems (the moral dilemmas). Thus, the aphorisms, that (paraphrasing) "It is equally important to ask the right questions, as it is to find the answers to the problems". Translated in the language of the scientific research world, this becomes that "it is important to design good experiments/ observation-study-setups and be very careful about the study designs."

Returning back to the issue of framing of moral problems, if the frame exists it is also because of our history: just like the moral intuitions - that at times help us survive and at times let us fall prey to frames- are due to our shared evolutionary history: so too the frames we use to cast and perceive the moral dilemmas are rooted in our history ( Nothing profound- what I mean by shared history is that someone formulated the problems in those terms, silly!!.)

I believe the problem is more with our inability to detach ourselves form frames and take more reasonable perspectives and know when to use our intuitions and when reason. As the saying goes "It is by the fortune of God that, in this country, we have three benefits: freedom of speech, freedom of thought, and the wisdom never to use either." Mark Twain (1835-1910). Alternately, another related saying that comes to mind(paraphrasing) " God, give us the ability to change what we can, humility to accept what we cannot and the wisdom to know what is what". We perhaps cannot change the historical frames or intuition that are in place, but we can definitely change our moral reasoning powers and following a developmental framework have compassion and understanding towards those who might not be employing the highest levels of moral reasoning.

Finally, If you are interested in my moral intuitions, I hypothesize, that the doctor (in the plane) would not be affected by Age, gender, race, potential, achievement etc would overcome his/ her Implicit Associations and would not try to find-out or gather-information deliberately to determine which life is more valuable- He/she would end up rushing between the patients and helping both at the same time; but if he/she is an intelligent doctor, would definitely save his/her life first, if suffering from Asthma, so that he/she could take care of others. This might seem like a rationalization (saving one's life so that one can help in whatever small way others), but one should use intelligence, even before emotions or moral instincts take center stage.

I believe that in the Airplane Scenario described above, there is a potential for a histrionic/hysteric reaction of the crew and travelers, as everyone tries to help the patients, (especially if no doctor is on-board) and that this may be the reverse of the bystander-effect like phenomenon I have hypothesized might happen in the Trolley problem (freezing and taking no action when a train is approaching towards five or six humans or towards a lone human). To make more sense of preceding line please read comments by Mc
Ewen on Mind Hacks post titled " "Mass Hysteria" closes school". Also, a solemn and personal request, please do not jump to conclusions, read or try to co-relate things out of context- or try to make sense of psychological concepts based on everyday usage of terms. If you do not understand any concepts mentioned above, read related literature and focus on that aspect alone- to the exclusion of other distracting eye-catchers. In case of any persisting confusions, feel free to ask your local psychiatrist/ psychologist/ psychology professor as to what those concepts mean.

PS: I believe that the post has become difficult-to-read, this was not done intentionally. Again, there might be spelling mistakes/ grammatical errors- don't get alarmed/ confused that this reflects racing thoughts etc- just point them out and I'll fix them- most of the times the editorial errors (some of them quite funny) are due to lack of time to revise/ lethargy to read. Also, this is also a part of my ongoing series, where I have posited that their may be gender differences in cognitive styles. Some of that may also be a required reading.

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Tuesday, December 05, 2006

Schizophrenia, Religion, Autism and the Indian culture (alternate title: Life, The Universe and Everything)

In continuation of my focus on the Schizophrenia-Autism dichotomy, I'll like to highlight two articles that seem to support my view.

The first is a blog post by, John Horgan, speculating whether religiosity is the inverse of autism.


The anthropologist Stewart Guthrie proposes that religious experiences—and particularly those involving visions or intuitions of a personal God--may stem from our innate tendency toward anthropomorphism, “the attribution of human characteristics to nonhuman things or events.” Guthrie called his book on this theory Faces in the Clouds, but he could have called it Jesus in the Tortilla.

Recent findings in developmental psychology dovetail with Guthrie’s theory. By the age of three or four all healthy children manifest an apparently innate ability to infer the state of mind of other people.

Psychologists postulate that autism stems from a malfunction of the theory-of-mind module. Autistics have difficulty inferring others’ thoughts, and even see no fundamental distinction between people and inanimate objects, such as chairs or tables. That is why autism is sometimes called “mind-blindness.”

But many of us have the opposite problem—an overactive theory-of-mind capacity, which leads to what the psychologist Justin Barrett calls “hyperactive agent detection.” When we see squares and triangles moving around a screen, we cannot help but see the squares “chasing” the triangles, or vice versa, even when we are told that the movements are random.


This is compatible with this blog's Schizophrenia-is-the-inverse-of-Autism theory for the following reasons:

1. Too much belief in agency in Schizophrenics (the hyperactive Agent detector conceptualized above) vs too less belief in agency in Autistics - characterized by me earlier as a Fantasy/Imagination Vs Reality orientation - has a direct relevance to whether one attributes anthropomorphic agency to non-living things and events (and thus Nature or God) or even fails to attribute intention to humans and animals and assumes them to be mere automata. I believe while a schizophrenic mindset can be characterized by a suspension-of-disbelief and too much causality and intention attribution (thus leading to the mindset compatible with religious/ spiritual leanings), the autistic mindset would lead to too much skepticism, too much even-causal-happenings-are-only-coincidental mindset and a reductionist, atheistic mindset that attributes no intention to humans, least of all animals, and believes that they are just advanced machines. I guess both are extremes of delusion, in one case one characterizes that as the GOD delusion; but the other extremist who sees no role of agency or intentionality (even in humans) is hauled as a great scientist!!

2. Another prominent dimension on which the Schizophrenics and autistic differ is the Literal-Metaphor dimension. I would like to frame that in terms of a Reference-Meaning use of a linguistic word and the consequent distinction in linguistics between a symbol as a referent of something and a symbol as signifying a meaning. For an excellent commentary on this difference, please do read this classical paper.

Meaning, let us remember, is not to be identified with naming. Frege's example of 'Evening Star' and 'Morning Star' and Russell's of 'Scott' and 'the author of Waverly', illustrate that terms can name the same thing but differ in meaning. The distinction between meaning and naming is no less important at the level of abstract terms. The terms '9' and 'the number of the planets' name one and the same abstract entity but presumably must be regarded as unlike in meaning; for astronomical observation was needed, and not mere reflection on meanings, to determine the sameness of the entity in question.

It is my contention that while the Schizophrenics are meaning obsessed; the Autistics are more reference obsessed, and thus have problems with metaphorical and figurative speech. From linguistics one can stretch the Meaning-Reference distinction and conceive of too much meaning orientation in schizophrenics ( and a meaningful life requires a GOD that gives a meaning to our lives) versus a nihilistic orientation in autistics that views the life/ evolution as purposeless. As many evolutionists famously claim - there is no meaning inherent in evolution, life or humans - rather that the question of meaning is invalid. Life just is.

3. Many schizophrenic delusions can be explained by an extreme manifestation of religiosity/ spirituality. As Szasz famously said, " If you talk to God, you are praying; if God talks to you you have schizophrenia". Both a belief in GOD and his ability to listen to our prayers (the religious belief) and the converse belief that God can talk to us , many times in symbolic ways, but sometimes in the form of actual auditory hallucinations are a manifestation of the same cognitive mechanism that attributes too much agency, causality and meaning. Many schizophrenics, indeed do suffer from delusion of Grandeur, whereby they think of themselves as GOD-like; or the delusion of persecution and paranoia whereby they are persecuted by Satan like evil figures. thus both hallucinations as well as the common delusions are explainable by the religiosity orientation. this time the GOD delusion is different - one believes that one is a god-head. In non-religious cultures, these being-GOD delusions may take the non-religious forms of being a famous historical person (who had great agency and effect on Human history and is presumably now active via the agency of the deluded schizophrenic), and the persecution delusions may not refer to Satan- but to their non-secular counterparts- the CIA and the government!! Of course the pathological forms of an Autistic mindset, that may have nihilistic orientations, and out of boredom and feelings of meaninglessness, may resort to meaningless acts of violence like the Columbine Massacres is one direction which needs further study.

I would now like to now draw focus on the Cultural differences post where I had speculated on the different incidences rates of Schizophrenia and Autism in the East Asian and American cultures based on the differential emphasis on holistic and contextual versus analytical and local processing and cognition and also presented some supporting evidence. The well documented religious/spiritual inclination of Oriental cultures versus the Scientific/materialistic orientation of the American and western cultures may be another factor that would affect and explain the relative incidences of Schizophrenia and Autism in these cultures.

In a culture like India, in which the people believe in 18 crore (180 billion) Gods and Deities, believe in reincarnation and believe that every human being is potentially divine, if a human errs towards an extreme and starts developing funny ideas of being a God herself, then that may not ring the alarm bells immediately. Rather some form of that delusion may even be encouraged (that is why in India names are kept after the Gods and Deities; while its rare to find the name Jesus in West, you can find millions of Rams in India). If the same GOD-delusion develops in an American, then his idea of being Jesus (or an angel) would definitely be detected early, lead to an earlier 'label' and an earlier hospitalization.

That said, I would now like to draw attention to an article today in the Times Of India, that pointed me to some more literature that unequivocally shows that not only are the incidence rates of schizophrenia less in India (and other third world (Asian) countries), the prognosis is manifold better in Indian patients as compared to American patients.

The success story of schizophrenics in India was propagated by mental health professionals based on the WHO research DOSMeD in 1979. This was carried out in 10 countries including developing ones such as India, Nigeria and Columbia. The findings showed striking differences in the prognosis of schizophrenia between developed and developing countries. The underlying causes for the diversity were associated more with family and social variables than clinical determinants. Majority of patients in developing countries showed remission over two years; only 50 per cent of them had a single relapse though around 15 per cent never recovered. Patient outcome in developing countries was superior to that in developed economies.


This difference has been hypothesized to be due to the strong family structure (and I do believe that it is an important factor) and the social cushion, support and acceptance that a family provides to the patient and shields him/her from stressful situations that may trigger a relapse.

This theory of a family-protective-advantage has come under attack recently, but I think the attack is flawed because it clubs countries not according to Cultures, but according to developmental status. Indeed, the other factor that may be affecting a better outcome in schizophrenic patients may be the cultural differences like the different cognitive/perceptual styles and a more tolerance for religious/spiritual/ mystical ideas. By shielding a person from stigmatization and isolation, based on eccentricities exhibited along these dimensions, one may be preventing or delaying relapse, and ensuring better outcome by not pushing the person over the edge. In the pats, it was not infrequent, for those who had psychotic experiences to be labeled as shamans and to be treated with respect, rather than stigma and isolation; thus ensuring that they were not exposed to social stresses in the future.

I have taken a somewhat deprecating attitude towards the extreme autistic orientation characterized by no intentionality, causality, spiritual beliefs, but I am a strong believer in the fact that though the extreme manifestation of Autism/Schizophrenia makes one dysfunctional, a pronounced autistic/ schizophrenic orientation does endow one with creative faculties - either to understand and manipulate the world (the Sciences) or to understand and manipulate the subjective experiences (the Arts) . In particular, as the readers of this blog would most likely be scientists, and because I belong the the scientific community and have failed to see how a scientific orientation is incompatible with an artistic/symbolic/spiritual orientation , I have taken a harder line for the extreme Atheist and nihilism zealots.

I believe one can, and must, utilize the different types of cognitive abilities these extreme manifestations and disorders caricature. Do let me know what your think!


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Savor the brain delicacies: encephalon 12 served hot and spicy at the AlphaPsy

The latest Encephalon, available at the AlphaPsy, is a mouth-watering treat that is not to be missed for life. It is not only delicious, but also healthy and wholesome.

You can jump to the main course, which starts with this blog's contributions, or you can savor the appetizers first like the recent research implicating entorhinal cortex with stimulus novelty detection and hippocampus with associative novelty detection based on comparing the stimulus with an expectation that is generated based on the last presented stimulus. This lines up neatly with earlier studies I have reported regarding three dissociated process of novelty, familiarity and recollection detection and the place and grid cells present in hippocampus and the associated cognitive map theory of the hippocampal function.

There are other delicacies ranging from the humpback whales spindle neurons to the self-fulfilling-prophecy effects that lead to bad luck for Vietnamese children born in bad luck years.

Recalling the feast has already made me hungry again, so I am going back to have a second course, or at least a few more desserts. Hope you manage to get there before me; don't complain if the stocks get exhausted!!



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The evolutionary trajectory of color vision

In a recent comment, a reader of this blog had highlighted some concerns regarding an evolutionary trajectory of color vision evolution that I had proposed in conjunction with the evolution of color terms in human languages and as a possible explanation for the linguistic trend. At that time, I had proposed a possible evolutionary scenario, without doing due diligence investigation of existing evolutionary theories of color vision, as my post had more of a linguistic and developmental focus and the evolutionary conjecture was just that- a conjecture, which, if found true, would lend more credence to my linguistic trend. Thanks to Andreas, I reviewed the literature on color vision evolution and was surprised to find some support for my theorization.

Before I discuss the color vision evolution, I'll strongly recommended reading two posts on the evolution of color vision and the evolution of retinal structures (more Avian focus here) , for getting some basic familiarities with the retinal structures involved in color vision and how they might have evolved.

To recap,

An animal has color vision if it has the capability of discriminating lights (scattered light as well as light sources) on the basis of the lights' spectral content, even when those lights are of equal subjective brightness.

The front end requirement for such a system is that the animal must have at least two different spectral classes of receptor, where each class is defined by the sensitivity of the receptor to light as a function of wavelength.


The above succinctly defines what we usually mean by color vision. You can either have a dichromatic color vision, when you have two differently tuned receptors to detect different light wavelengths and the different signal combinations from these receptors yield different hues; or you can have trichroimatic / tetrachromatic vision where three/four independent color signals are combined to yield an entire Hue range. One familiar with the RGB color system used in computers, would note that it is based on the assumption of 3 pure colors, which can be mixed in different amounts to yield most of the color hues we see on the monitor.Pigeons, and birds in general, have a tetrachromatic color vision.

Now for some basic visual circuitry:

The retinal structures involved in vision, in mammals, are, pohotorecptors (classified as cones and rods), horizontal, bipolar, amaracine and ganglion cells.


However, for all vertebrates (mammals as well as reptiles and birds) and invertebrates as well, the receptor mechanism is conserved and is basically the same and we will discuss that first:

The first step in the transduction of light energy to a neural signal is the light-induced isomerization (change of shape) of a chromophore, specifically a vitamin A derivative. Each chromophore is bound to a membrane protein called an opsin. The main function of the opsin is to change shape after light absorption triggers the isomerization of the chromophore: the opsin is an enzyme that is activated by the chromophore's isomerization. However, because of the linkage between the opsin and the chromophore, the opsin also serves to tune the wavelength dependence of the light induced isomerization reaction in the chromophore. That is, the chromophore's sensitivity to light at a given wavelength is established in part by the opsin--different opsins (i.e. opsins with different amino acid sequences) bound to identical chromophores will have different absorption probabilities at each wavelength. The result is that photoreceptors which express the gene for only one type of opsin will form a different class than photoreceptors that express a gene coding for a different opsin. Although there are other mechanisms that animals could use to differentiate photoreceptor classes (most notably some animals use more than one chromophore, and many vertebrates have colored oil droplets that screen individual receptors) it seems that the expression of only one of their possible opsin coding genes in each receptor is the mechanism that all animals use.



The above clarifies, that in mammals, we associate color vision with cones or specialized photoreceptors that contain a single pigment and are responsive to a single wavelength range. In reptiles, we also have double cones, wherein, two photopigment/ receptors are part of the same cell and then there are other mechanism like oil droplets that are also involved in color vision (but thankfully not in mammals). Rods are also a type of receptors, tuned to a frequency, but we normally do not associate rods with color vision, because they are usually used for night vision and their signals are not combined to create the color hue; yet a limited form of monochromatic color vision is possible by having a combination of one rod and one cone receptor types.


Next we need to differentiate between the rhabodermic eyes of invertebrates (based on r-opsin and the ciliary eyes of vertebrates based on c-opsins. Pharyngula does an excellent job here.

Eyes can be further categorized as rhabdomeric or ciliary by the nature of the cellular elements that make up the photoreceptors, by the kind of opsin molecule used to transduce the light signal, and by the signaling pathway used to convert a conformation change of the opsin molecule into a change in the electrical potential across the cell membrane.

As many accounts of color vision evolution focus on the phylogentic tress of opsin genes evolution to make their case, it is important to distinguish between the levels of analysis. All the known Opsin genes can be classifies in seven sub-families: two of these the r-opsin families and the c-opsin families are pertinent to, and expressed in, the photorecptors found in invertebrates and vertebrates respectively.



Thus, if one wants to focus on mammal color vision evolution, one needs to focus on c-opsins mostly. Many studies have been conducted over these and the phylogentic data indicates that the vertebrate opsins too form a neat tree with five sub-families relevant for (color) vision and 3 other sub-families having non-visual functions.

Thus, in mammals we have a five types of opsins : one rhodopsin-type and expressed in rods, and four other chromatic types (detecting Red, Blue, Green and U/V colors) and expressed in cones.

One should pause here and note that the human S(short) or blue receptor actually belongs to the U/V (S) family; while the human L (red) and M (green) receptors both belong to the Red (L) family.

These 5 opsin families (Red, Gree, Blue, U/V and Rhodipsin)have been variously characterized as (L, ML, MS, S and Rh) or as(RH1, RH2, LWS, SWS1 and SWS2).

With this background, information, we can now go straight to the heart of the problem: the evolutionary trajectory of these different receptors / opsins and how the color vision evolved in humans. I'll limit the discussion here to mammals first and then to primates , as my original thesis that color terms evolution follows the color vision evolution requires the analysis to happen only in that time frame in which linguistic abilities make sense. Assuming some proto-language in Apes and primates, it is reasonable to expect that whatever sequence of color terms we see in languages, would reflect the successive levels of color vision as experienced by Primates, and would be independent of how color was perceived in invertebrates. (I'm sure no one contends that the color terms of human languages should capture the early chromatic experiences of invertebrates).

Although I do not buy the bottleneck theory of Mammal evolution -stock, barrel and lock - I believe we can take that as a reasonable starting point. It posits that mammals were reduced to being a nocturnal burrowing species during the age pf the dinosaurs and thus were reduced to having just the rods, and lost the earlier, cones, double cones and oil pigments that reptiles still have. In any case, in mammals, rods seem to be older and more conserved than cones. (Pat on the back: one claim originally made defended to satisfaction!!)

Amongst vertebrates, the rod opsin seems to be the most conserved; cone opsins have arisen principally by duplication and subsequent mutation of the rod opsin gene.

Also,

Which of the two primary classes, rods or cones, is the ancestral photoreceptor? Given the tremendous variation seen photoreceptors across vertebrate and invertebrate species, this in not an easy question to answer based on simple phylogenetic assumptions. In addition, it is often difficult to clearly distinguish certain rod and cone types from each other, or classify them into one or the other category. Rods appear to be relatively more conserved in vertebrates in terms of pigments and structure than cones, and therefore could be considered the more ancestral form. However, rods in some respects are more morphologically complex than cones, having developed extreme sensitivity (capable of detecting as little as one photon of light).


Now,coming to the evolution(or re-evolution) of the cones or the chromatic system in mammals, it is instructive to pause here and note that having three cones does not necessarily mean that the two species will have the same qualia of color hues.

If we restrict ourselves to animals which have the same number of receptor classes, might we expect that their color vision systems are equivalent? The answer is a resounding no. Let's compare the color vision systems of two animals that both have three photopic (e.g. active under bright illumination) photoreceptor classes. One is the human, the other is the honey bee (specifically the worker--I don't know how the other castes are endowed). Does anybody here think that what a bee sees when it looks at a rainbow has the same appearance as what we see? We'll ignore optical polarization (which the bee is sensitive to and we're not) and focus on what we can infer about "color" based on, among other things, our knowledge of the bee's receptor classes. To begin with, at the inside of the rainbow where the violet-appearing light fades off to invisibility for us, the bee will still see more rainbow. On the outside, where we see red, the bee would see nothing for although bees have an ability to see what for us is UV, we have the ability to see what bees might call infrared.

Also, it is instructive to note here how a higher level chromatic vision (dichromatic for instance) may arise form a lower level chromatic vision (monochromatic in this example). Although, along with the photoreceptors, we will need additional supporting neural wiring, in both the retina and the brain, for the opponent-processing mediated color perception to take place, we will restrict the discussion to the emergence of a new photoreceptor.

A new photoreceptor, may come into existence by a duplication and polymorphisms of an existing receptor (opsin) gene. The new receptor would have a slightly different frequency sensitivity than the original receptor and, by selectively expressing these two genes in different receptors, we can have two types of receptors. By processing and combining the two types of signals, one can now get dichromatic vision, from the original monochromatic vision.

Much confusion, in primate color vision evolution, depends on the fact that one takes as base the other mammals like dogs, and their blue-yellow world as a baseline from where to start. It should be emphasized that even though dogs may currently have two receptors, tuned to detect blue and yellow, we cannot conclude form that anything about humans or ancient ancestral mammals. In the human ancestry lineage, the dichromatic phase may have involved Red-Green perception. This is evident form the bee-human trichromatic example given above.

A very good paper summarizing the latest research on primate color evolution concludes that their are five types of primate color vision systems- beginning with a Monochromatic (L opsin only)_ system in nocturnal primates to a S + M+L (multiple copies) trichromatic system in humans.



It is interesting to note here that the human Green evolved, by replication and polymerization of the Red opsin present on the X chromosome. From the hierarchy of primate color systems, it is reasonable to conclude, that initially when we were nocturnal primates, we had a dysfunctional S-opsin gene and a functional L gene- conferring us the ability to perceive the red qualia to some extent.

In diurnal prosimians, the S become functional and they have two qualia- that of red and blue.

In the new world monkeys, the L gene is polymorphic (it is on X chromosome and as explained in the paper, if we have two alleles for that L gene, that encode for slightly different frequencies, then as females have two X chromosomes, they can have both the alleles; the males meanwhile have only one X chromosome; so at at a time they can have only one of the alleles present. By X chromosome inactivation process, all cells of a female new world monkey, will have only one of the alleles; but different cells may have different alleles expressed and thus, the females may have 3 types of receptors (one S type and two L types), thus endowing them with trichromatic vision. The Males meanwhile will have dichromatic vision, but as the gene is polymorphic, we will differences in their dichromatic perceptions. This is exactly what is observed.

The old world monkeys, have the full apparatus for trichromatic vision- with one S and two L genes. The second L (or rather M as it detects green) gene was formed by replication and polymorphisms of the L gene that detected red. thus, they had the qualia of Red, Blue and Green.

Lastly, the humans, are more or less the same as old world Monkeys; but their L gene shows polymorphisms. This has the effect of making some females tetrachromatic (as this polymorphisms will only affect females- only they have two copies of X chromosome) and it seems , that by fortuitous replication, we might get a fourth cone type in all humans. Till then, this polymorphisms will explain some of the color perception differences that we may exhibit.

Suffice it to say, that the evolution of color terms should follow the same trajectory- with Black and White (rod based) color terms preceding Red, Blue, Green and Yellow color terms.

A final note of caution: only receptor types do not guarantee that the qualia experienced would change. In an experiment with mice, in which the mice were endowed with human pigments, they could not still learn to distinguish Red, as presumably the latter opponent-processing wiring, required for that qualia generation was not present/ couldn't develop.

Thats all for now. Hope you found this post Eye opening!! Do let me know via comments of any incompatible/recent evidences and arguments.

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Friday, December 01, 2006

Abstract vs Concrete: the two genders?( the catogorization debate)

In my previous posts I have focussed on distinctions in cognitive styles based on figure-ground, linear-parallel, routine-novel and literal-metaphorical emphasis.

There is another important dimension on which cognitive styles differ and I think this difference is of a different dimension and mechanism than the figure-ground difference that involves broader and looser associations (more context) vs narrow and intense associations (more focus). One can characterize the figure-ground differences as being detail and part-oriented vs big picture orientation and more broadly as analytical vs synthesizing style.

The other important difference pertains to whether associations and hence knowledge is mediated by abstract entities or whether associations, knowledge and behavior is grounded in concrete entities/experiences. One could summarize this as follows: whether the cognitive style is characterized by abstraction or whether it is characterized by a particularization bias. One could even go a step further and pit an algorithmic learning mechanism with one based on heuristics and pragmatics.

It is my contention that the bias towards abstraction would be greater for Males and the left hemisphere and the bias towards Particularization would be greater for Females and the right hemisphere.

Before I elaborate on my thesis, the readers of this blog need to get familiar with the literature on categorization and the different categorization/concept formation/ knowledge formation theories.

An excellent resource is a four article series from Mixing Memory. I'll briefly summarize each post below, but you are strongly advised to read the original posts.

Background: Most of the categorization efforts are focussed on classifying and categorizing objects, as opposed to relations or activities, and the representation of such categories (concepts) in the brain. Objects are supposed to be made up of a number of features . An object may have a feature to varying degrees (its not necessarily a binary has/doesn't has type of association, one feature may be tall and the feature strength may vary depending on the actual height)

The first post is regarding classical view of concepts as being definitional or rule-bound in nature. This view proposes that a category is defined by a combination of features and these features are of binary nature (one either has a feature or does not have it). Only those objects that have all the features of the category, belong to a category. The concept (representation of category) can be stored as a conjunction rule. Thus, concept of bachelor may be defined as having features Male, single, human and adult. To determine the classification of a novel object, say, Sandeep Gautam, one would subject that object to the bachelor category rule and calculate the truth value. If all the conditions are satisfied (i.e. Sandeep Gautam has all the features that define the category bachelor), then we may classify the new object as belonging to that category.

Thus,

Bachelor(x)= truth value of (male(x))AND(adult(x))AND(single(x))AND(human(x))

Thus a concept is nothing but a definitional rule.

The second and third posts are regarding the similarity-based approaches to categorization. These may also be called the clustering approaches. One visualizes the objects as spread in a multi-dimensional feature space, with each dimension representing the various degrees to which the feature is present. The objects in this n-dim space, which are close to each other, and are clustered together, are considered to form one category as they would have similar values of features. In these views, the distance between objects in this n-dim feature space, represents their degree of similarity. Thus, the closer the objects are the more likely that they are similar and the moire likely that we can label them as belonging to one category.

To take an example, consider a 3-dim space with one dimension (x) signifying height, the other (y) signifying color, and the third (z) signifying attractiveness . Suppose, we rate many Males along these dimensions and plot them on this 3-d space. Then we may find that some males have high values of height(Tall), color(Dark) and attractiveness(Handsome) and cluster in the 3-d space in the right-upper quadrant and thus define a category of Males that can be characterized as the TDH/cool hunk category(a category that is most common in the Mills and Boons novels). Other males may meanwhile cluster around a category that is labeled squats.

Their are some more complexities involved, like assigning weights to a feature in relation to a category, and thus skewing the similarity-distance relationship by making it dependent on the weights (or importance) of the feature to the category under consideration. In simpler terms, not all dimensions are equal , and the distance between two objects to classify them as similar (belonging to a cluster) may differ based on the dimension under consideration.

There are two variations to the similarity based or clustering approaches. Both have a similar classification and categorization mechanism, but differ in the representation of the category (concept). The category, it is to be recalled, in both cases is determined by the various objects that have clustered together. Thus, a category is a collection or set of such similar object. The differences arise in the representation of that set.

One can represent a set of data by its central tendencies. Some such central tendencies, like Mean Value, represent an average value of the set, and are an abstraction in the sense that no particular member may have that particular value. Others like Mode or Median , do signify a single member of that set, which is either the most frequent one or the middle one in an ordered list. When the discussion of central tendencies is extended to pairs or triplets of values, or to n-tuples (signifying n dim feature space) , then the concept of mode or median becomes more problematic, and a measure based on them, may also become abstract and no longer remain concrete.

The other central tendencies that one needs are an idea of the distribution of the set values. With Mean, we also have an associated Variance, again an abstract parameter, that signifies how much the set value are spread around the Mean. In the case of Median, one can resort to percentile values (10th percentile etc) and thus have concrete members as representing the variance of the data set.

It is my contention that the prototype theories rely on abstraction and averaging of data to represent the data set (categories), while the Exemplar theories rely on particularization and representativeness of some member values to represent the entire data set.

Thus, supposing that in the above TDH Male classification task, we had 100 males belonging to the TDH category, then a prototype theory would store the average values of height, color and attractiveness for the entire 100 TDH category members as representing the TDH male category.

On the other hand, an exemplar theory would store the particular values for the height, color and attractiveness ratings of 3 or 4 Males belonging to the TDH category as representing the TDH category. These 3 or 4 members of the set, would be chosen on their representativeness of the data set (Median values, outliers capturing variance etc).

Thus, the second post of Mixing Memory discusses the Prototype theories of categorization, which posits that we store average values of a category set to represent that category.

Thus,

Similarity will be determined by a feature match in which the feature weights figure into the similarity calculation, with more salient or frequent features contributing more to similarity. The similarity calculation might be described by an equation like the following:
Sj = Si (wi.v(i,j))
In this equation, Sj represents the similarity of exemplar j to a prototype, wi represents the weight of feature i, and v(i,j) represents the degree to which exemplar j exhibits feature i. Exemplars that reach a required level of similarity with the prototype will be classified as members of the category, and those fail to reach that level will not.


The third post discusses the Exemplar theory of categorization , which posits that we store all, or in more milder and practical versions, some members as exemplars that represent the category. Thus, a category is defined by a set of typical exemplars (say every tenth percentile).

To categorize a new object, one would compare the similarity of that object with all the exemplars belonging to that category, and if this reaches a threshold, the new object is classified as belonging to the new category. If two categories are involved, one would compare with exemplars from both the categories, and depending on threshold values either classify in both categories , or in a forced single-choice task, classify in the category which yields better similarity scores.

Thus,

We encounter an exemplar, and to categorize it, we compare it to all (or some subset) of the stored exemplars for categories that meet some initial similarity requirement. The comparison is generally considered to be between features, which are usually represented in a multidimensional space defined by various "psychological" dimensions (on which the values of particular features vary). Some features are more salient, or relevant, than others, and are thus given more attention and weight during the comparison. Thus, we can use an equation like the following to determine the similarity of an exemplar:
dist(s, m) = åiai|yistim - ymiex|


Here, the distance in the space between an instance, s, and an exemplar in memory, m, is equal to the sum of the values of the feature of m on all of dimensions (represented individually by i) subtracted from the feature value of the stimulus on the same dimensions. The sum is weighted by a, which represents the saliency of the particular features.


There is another interesting clustering approach that becomes available to us, if we use an exemplar model. This is the proximity-based approach. In this, we determine all the exemplars (of different categories) that are lying in a similarity radius (proximity) around the object in consideration. Then we determine the category to which these exemplars belong. The category to which the maximum number of these proximate exemplars belong, is the category to which this new object is classified.

The fourth post on Mixing Memory deals with a 'theory' theory approach to categorization, and I will not discuss it in detail right now.

I'll like to mention briefly in passing that there are other relevant theories like schemata , scripts, frames and situated simulation theories of concept formation that take into account prior knowledge and context to form concepts.

However, for now, I'll like to return to the prototype and exemplar theories and draw attention to the fact that the prototype theories are more abstracted, rule-type and economical in nature, but also subject to pragmatic deficiencies, based on their inability to take variance, outliers and exceptions into account; while the exemplar theories being more concrete, memory-based and pragmatic in nature (being able to account for atypical members) suffer from the problems of requiring large storage/ unnecessary redundancy. One may even extrapolate these differences as the one underlying procedural or implicit memory and the ones underlying explicit or episodic memory.




There is a lot of literature on prototypes and exemplars and research supporting the same. One such research is in the case of Visual perception of faces, whereby it is posited that we find average faces attractive , as the average face is closer to a prototype of a face, and thus, the similarity calculation needed to classify an average face are minimal. This ease of processing, we may subjectively feel as attractiveness of the face. Of course, male and female prototype faces would be different, both perceived as attractive.



Alternately, we may be storing examples of faces, some attractive, some unattractive and one can theorize that we may find even the unattractive faces very fast to recognize/categorize.








With this in mind I will like to draw attention to a recent study that highlighted the past-tense over-regularization in males and females and showed that not only do females make more over-regularization errors, but also these errors are distributed around similar sounding verbs.

Let me explain what over-regularization of past-tense means. While the children are developing, they pick up language and start forming the concepts like that of a verb and that of a past tense verb. They sort of develop a folk theory of how past tense verbs are formed- the theory is that the past tense is formed by appending an 'ed' to a verb. Thus, when they encounter a new verb, that they have to use in past tense (and which say is irregular) , then they will tend to append 'ed' to the verb to make the past tense. Thus, instead of learning that 'hold', in past tense becomes 'held', they tend to make the past tense as 'holded'.

Prototype theories suggest, that they have a prototypical concept of a past tense verb as having two features- one that it is a verb (signifies action) and second that it has 'ed' in the end.

Exemplar theories on the other hand, might predict, that the past tense verb category is a set of exemplars, with the exemplars representing one type of similar sounding verbs (based on rhyme, last coda same etc). Thus, the past tense verb category would contain some actual past tense verbs like { 'linked' representing sinked, blinked, honked, yanked etc; 'folded' representing molded, scolded etc}.

Thus, this past tense verb concept, which is based on regular verbs, is also applied while determining the past tense of irregular verb. On encountering 'hold' an irregular verb, that one wants to use in the past tense, one may use 'holded' as 'holded' is both a verb, ends in 'ed' and is also very similar to 'folded'. While comparing 'hold' with a prototype, one may not have the additional effect of rhyming similarity with exemplars, that is present in the exemplar case; and thus, females who are supposed to use an exemplar system predominantly, would be more susceptible to over-regularization effects as opposed to boys. Also, this over-regularization would be skewed, with more over-regularization for similar rhyming regular verbs in females. As opposed to this, boys, who are usinbg the prototype system predominantly, would not show the skew-towards-rhyming-verbs effect. This is precisely what has been observed in that study.

Developing Intelligence has also commented on the same, though he seems unconvinced by the symbolic rules-words or procedural-declarative accounts of language as opposed to the traditional confectionist models. The account given by the authors, is entirely in terms of procedural (grammatical rule based) versus declarative (lexicon and pairs of past and present tense verb based) mechanism, and I have taken the liberty to reframe that in terms of Prototype versus Exemplar theories, because it is my contention that Procedural learning , in its early stages is prototypical and abstractive in nature, while lexicon-based learning is exemplar and particularizing in nature.

This has already become a sufficiently long post, so I will not take much space now. I will return to this discussion, discussing research on prototype Vs exemplars in other fields of psychology especially with reference to Gender and Hemisphericality based differences. I'll finally extend the discussion to categorization of relations and that should move us into a whole new filed, that which is closely related to social psychology and which I believe has been ignored a lot in cognitive accounts of learning, thinking etc.

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