Monday, August 27, 2007

Darwinian Linguistic Evolution

There is a paper by Oudeyer and Kaplan, which discusses the evolution of languages in Darwinian terms. That is a refreshingly new (to me!) take on how languages may evolve. It applies the same Darwinian principles of heritability, variation and selection to individual phonetic words as well as associations between words and meanings.

The article makes use of computer simulations to inform their theory. Some of the take home from that article are:

  • For Linguistic coherence to evolve (that is one word referring to same meaning for different agents), the replication principle most suited is whereby the most frequently encountered word is repeated and thus gets fixated in the population. This scores over the use-the-last-heard phoneme rule and use-the-phoneme-as-per-frequency-in-usage rules.
  • The phonemes that can be easily confused (are liable to mutate more) with nearby phonemes get selected against and thus, selection leads to implicit evaluation whereby those phonemes that do not mutate (or mutate less) are preferred and get fixated.
  • In a population with agents coming and leaving, the population flux ensures that optimal words are used and sub-optimal done away with.
  • The linguistic phonemes (or words) that are used to represent concepts, break the acoustic space in such a way that their is least scope for confusion amongst the phonemes.
  • A trade-off happens between linguistic distinctively and robustness. Some words are long enough that they can mutate more, but are not easily confusable. Other frequently used words are short and do not mutate easily, but if they mutate than more confusion of meaning arises.

There are more such interesting information nuggets in the paper. So why don't you have a look at the original paper itself.

Hat tip: Babel's Dawn.

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Second Life of Craig J. Phillips

No, I am not talking about the computer game Second life! This post is regarding Mr. Craig J. Phillips, who suffered traumatic brain injury and not only survived, but thrived and currently maintains a blog. He recently contacted me via commenting on this blog and I would like to quote from that and encourage readers to visit his blog and discover with him his journey that was akin to a second life.


My name is Craig J. Phillips. I am a traumatic brain injury survivor and a master’s level rehabilitation counselor. I sustained an open skull fracture with right frontal lobe damage and remained in a coma for 3 weeks at the age of 10 in August of 1967. I underwent brain and skull surgery after waking from the coma. Follow-up cognitive and psychosocial testing revealed that I would not be able to succeed beyond high school. In 1967 Neurological Rehabilitation was not available to me, so I had to teach myself how to walk, talk, read, write and speak in complete sentences. I completed high school on time and went on to obtain both my undergraduate and graduate degrees. For an in depth view of my process please read my post, http://secondchancetolive.wordpress.com/2007/02/18/my-journey-thus-far/

Through out my lifetime I developed strategies to overcome many obstacles and in so doing I have achieved far beyond all reasonable expectations. On February 6, 2007 at the encouragement of a friend I created Second Chance to Live. Second Chance to Live, which is located at http://secondchancetolive.wordpress.com presents topics in such a way to encourage, motivate and empower the reader to live life on life’s terms. I believe our circumstances are not meant to keep us down, but to build us up. As a traumatic brain injury survivor, I speak from my experience, strength and hope. As a professional, I provide information to encourage, motivate and empower both disabled and non-disabled individuals to not give up on their process.

Please encourage your readers to visit Second Chance to Live at http://secondchancetolive.wordpress.com

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Wednesday, August 22, 2007

Disscoiation between analgesic and addictive effects of pain-killers

Common pain-killers like Morphine have both pair-relieving as well as tolerance and addictive effects. Opiates, it had been theorized earlier, were able to relieve pain via a mechanism that involved the neurotransmitter Serotonin. For the first time , this has been decisively proved to be so, by examining the effects of pain-killer on mice that were engineered to have the serotonin producing gene, Lxmb, silenced in the 5-HT neurons. As such these mice completely lacked serotonin in their brains.

It was found that these mice exhibited more sensitivity to pain and also morphine, or other opiates, were not able to relive the pain in these mice. On the other hand the addictive effects of morphine remained intact.

I am tempted to conjecture further. Is it the case that psychological and physical pain share the same neural substrates? Remember that low levels of serotonin cause depression, in which the sensitivity to psychological pain is elevated. this is similar to the fact that the sensitivity for physical pain is heightened in mice lacking serotonin.I am further tempted to stick my neck out and recommend that the experiment be perormed with mice that have dopamine producing neurons silenced in the brain. If such mice can survive to adulthood, would they exhibit the analgesic effects of morphine, but not its addictive effects? anyway this dissociation between analgesic and addictive effects of morphine would have serious pharmacological effects.

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