October 04, 2007

From Ruth Rosin:

Re: Built-in brain “templates” may clue tots to threats (Sept. 18): All individual traits (including behavioral traits) develop under inseparable effects of both genes & environment. There is no such thing as genetically predetermined tendencies to develop specific behaviors.

Human babies do not begin to develop at birth. They begin to develop at conception, and they experience moving, and kicking their limbs, as well as sucking their thumbs before they are born. Obviously their brain is not a tabula rasa when they are born. But the idea that they have a genetically predetermined tendency to learn to fear spiders, but not dogs, is utterly preposterous; all the more so since wild predetors the size of dogs are far more dangerous to humans than spiders.

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Anonymous Anonymous said...

I've not read the paper yet, but seems somewhat weak from the article. That icon of a spider has not much more similarity to a real spider, than one of those icons on toilet doors, indicating whether it's a men's or women's toilet, brings to real humans, so I think it can't really tell much about instincts. Real spiders would be found in real life in a whole bunch of different angles, with different positions of their legs, standing in their web or walking and jumping around. In these situations,they would not necessarely resemble a classical icon of a spider much more than the icon of an ant some nonspecific splat with "legs". A more likely "mental template" to fear would be "leggy dots", specially "floating" or moving ones. If an innate fear of spiders does exist, it would probably not be so tuned to spiders specifically, but likely to other similar animals as well, such as scorpions and insects, almost in general.
I'm also skeptical about the claim on the gene reaching fixation on only 20 or 30 generations. Haldanes's calculations on substitutions costs estimate that any given gene, under relatively strong selection, reaches fixation on about 300 generations.
If babies are more prone to look at the normal spider icon than to a scrambled one, perhaps we have a innate preference to symetrical figures in general, over assymetrical ones, a difference that may have not been the case with scrambled or non-scrambled flowers, I think. Perhaps an innate bias to have the attention more grabed by the perception of symetric forms is all that is needed to eventually develop a fear of spiders, or dangerous tiny animals in general. "If it's symetrical, and moves, may be dangerous". I also have my doubts on the degree of eyesight accuracy an infant of this age has, I don't know for sure, but it's not until a certain age that they all mature their eyes, before that, they're all somewhat myopes. (But it's very likely that this point has been considered by the researchers.)

October 17, 2007 11:54 AM  

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