Tuesday, October 31, 2006

color memory, stroop test and models of working memory

BPS research digest as well as Mixing Memory have both commented on a recent study that showed that our memory of colors associated with a particular object, affects our actual color perception.

As per this study, as we have normally only seen a yellow banana and that color association is quite strong in our minds, hence when we perceive a 'different' colored banana, we are bound to see it more yellowish than is the actual hue in which the different color banana is presented.

Basically, they used 2 extremely good experiments that show that when viewing a banana (which is generally yellow), the yellow color perception is automatically activated in our brains: thus a gray matched banana would appear yellowish; while the task that requires matching a pink banana to a gray background would result in a bluish-gray banana, as blue is the opponent color for yellow and blue is added to the background gray to compensate for the memory-activated yellow color perception.

It is interesting to draw parallels here with the stroop test. In this test, color words like 'red', 'yellow' etc also appear to invoke automatic activation of the corresponding color in the brain and thus interferes with the correct naming of the actual color in which the color word is presented. Developing Intelligence has a very interesting and promising post, in which he explores the current research and computation models, that seem to suggest that the mechanism underlying stroop interference is not directed inhibition of prepotent responses, but lateral excitation among color and linguistic perception modules, with color perception area of the brain being always activated when a color linguistic term is presented and in the incongruent trials more activation seen in this to-be-ignored module as the conflicting activations of color - one due to the actual color of the word and the other due to the color perception activated by the linguistic color word ('red' ) both competing against each other lead to more activation. This is in contrast to the view that the more activation is due to directed inhibition . The new explanation advocated seems also to fit with the brain anatomy, with there being only local inhibition processes and is reconcilable with a lack of long range inhibiting pathways in the neocortex.

Thus to me, it seems more and more possible that stroop effect may be due to actual 'yellowish' hue perception in brain on watching the linguistic term 'yellow'. I know that the two examples are not the same-- a yellow banana actually has yellow color and thus its memory may affect the perception of a strange colored banana; but maybe the 'yellow' linguistic term is also somehow related in our mind very strongly with actual yellow hue perception and maybe we are all synaesthetic to the extent that all of us literally see the linguistic color terms in color rather than in black-and-white (or whatever the text color).



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Self-awareness in elephants!

As per a recent news report, it has been found that elephants too have self-awareness. The test used was that of identifying a spot on their body, when in front of mirror and observing their behavior when in front of mirror. This is a classical measure of self-awareness, though some disagree about its importance.

After apes and dolphins, Elephants also seem to have self-awareness!

The original study is available at PNAS and offers some convincing data.

Update: The video of the elephant touching the mark on her body after seeing her reflection in mirror is available at the Neurohilosopher.

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Monday, October 30, 2006

The Synapse, spooky issue 10 : unleashed just now to scare your wits out!

The Neurocritic, has just unleashed a very viral and resistant new strain of Synapse, that is bound to keep you hooked to your monitors for quite some time. Captivating visuals accompany the best in Science reporting - from the Dilbert-Spasmodic Dysphonia connection to an exhortation to Goalies to keep their eyes on the puck.

If you do get infected , remember I warned you in advance!

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A new issue of the Tangled Bank

Josh, of Thoughts From Kansas, has just published a brand new edition of the Tangled Banks, despite a very short notice. Kudos to him, for compiling such a nice collection of articles., some of which are focussed on Evolution.

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Friday, October 27, 2006

Hope for the elderly: Cognitive programs that keep you fit

For those worried about Age Related Cognitive Decline or Senile dementia or the Alzheimer's, there is hope round the corner. A study published in PNAS, has demonstrated that a brain plasticity-based training that involved a 1 hr workout, 5 days a week, for 8-10 weeks, led to a significant improvement both on the training exercises as well as on measures of general auditory memory as measured by the global auditory memory scale of RBANS. The exercises were relatively simple, like syllable matching and identification; or narrative comprehension and word span; but were focused on enhancing the brain's plasticity.

While the effect of cognitive training and workout on childhood cognitive development is relatively well-documented, the effects for adults and aging population are relatively less established. Another similar study has recently shown that even computer based interventions can lead to significant increases in cognitive functioning, even for the seriously incapacitated population like those suffering from Alzheimer's. This should be of some cheer to those who are tormented by the thoughts of incapacitation in senility. If we give our brains a proper workout, we can reverse, or at least limit, the presumably 'inevitable' cognitive decline with age.

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A gene that affects episodic memory?

A tantalizing study, published in Science, indicates that a SNP in a single gene KIBRA, could lead to a difference of as big as 25% in the outcome of a free recall test measuring the episodic memory. The KIBRA gene is expressed in the medial temporal lobe (the hippocampal region) and using fMRI the authors were able to demonstrate different levels of activation in this brain area for the carriers versus non-carriers of the T allele when they were engaged in a retrieval task.

Human memory is a polygenic trait. We performed a genome-wide screen to identify memory-related gene variants. A genomic locus encoding the brain protein KIBRA was significantly associated with memory performance in three independent, cognitively normal cohorts from Switzerland and the United States. Gene expression studies showed that KIBRA was expressed in memory-related brain structures. Functional magnetic resonance imaging detected KIBRA allele–dependent differences in hippocampal activations during memory retrieval. Evidence from these experiments suggests a role for KIBRA in human memory

This is an important work and could lead to much insight on the memory formation mechanisms involved.

Hat Tip: Small Gray Matters

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Thursday, October 26, 2006

Gender bias in Math skills : a case of Traits Vs. Environment/Effort feedback?

A recent news article reports on a study that demonstrates that the gender bias in Math abilities may be due to environmental and cultural effects - specifically as a result of the negative self- perception garnered by the activation of the negative stereotype of women as having grossly inferior mathematical abilities than men.

The experiment involved giving 220 female study participants bogus scientific explanations for alleged sex differences in math and then having them write math tests. Those who were given a 'nature' explanation - that women have differential genetic composition than men and the cause of their low maths abilities was genetic and gender based - performed poorly on the Math tests compared to the group that was told that their math skills depended on how they were raised and were given a 'nurture' explanation and an experiential account of the sex differences such as math teachers treating boys preferentially during the first years of math education.

In the control condition some females were told that no sex differences exist while another group was reminded (primed) of the stereotype about female math under-achievement.

The worst performance was for genetic explanation females, followed by 'stereotype primed' females. Those who were given an experiential explanation performed as well or better than the control group that received the feedback that there were no sex differences in Math abilities.

While the authors analyze and explain the results in terms of the 'Stereotype theory' - that genetic explanations lead to more negative stereotypes and that activation of the negative stereotype affects performance- a more parsimonious explanations is that the differences can be explained by the same differential outcomes that are observed in people who have a genetic or trait-like versus an effort-driven or skill-like view of abilities. I have discussed previously how these differential view of abilities may develop and the experiment above has just the right conditions to induce such a differential view.

Those who were given a genetic explanation of sex differences in math abilities, may have formed a trait-like view of Math ability and were prone to see the ability as stable, genetic and immutable. This is the same view of math ability that would be formed if they had been given generic feedback - like "you are a math prodigy".

Those who had been given experiential explanations of sex differences would have been more prone to form a skill-like view of math abilities and assume that the ability could be improved and honed based on environmental inputs like proper teaching, guidance, strategy or efforts. This would have been the case if they had been given 'specific' feedback - like "you solved this math problem very well this time".

It is evident that a large part of the difference in the math test results observed in genetic vs experiential explanation conditions can be explained by the different view about math abilities that these experiments had induced. Those who were having the trait-like view of math ability would get frustrated while tackling a difficult problem and would be less resilient and effort-full while tackling the latter, more easy, problem on the test; as they would have formed a negative self-perception as one who has little mathematical talent. On the other hand, those who had been induced to form a skill-like view of math ability, would have been more resilient and effort-full when tackling latter problems, despite some early failures, as a failure would not have led to a resigned sate of mind, but would have only resulted in a belief that the strategies or effort or earlier training had not been sufficient to solve the particular problem.

It is not my contention that negative stereotype activation has no role to play- priming with stereotype words does lead to measurable effects on performance - but in this case, even if the stereotype activation is involved, the stereotype may be instrumental in activating the differential view of mathematical abilities and its effects mediated by the effects that such views have on test performances.

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Monday, October 23, 2006

Encephalon #9 is out!

The latest edition of that fantastic brain carnival called Encephelon is now out. The ninth edition has been very nicley presneted by Dan at the Migrations.

There are special focus sections on Learning, Perception, Autism and Neuroscience, so have your pick and enjoy!

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