Friday, August 12, 2005

Innate Information and Behaviour

Suppose that mice will scurry away whenever they perceive a hawk-shaped shadow. It seems that there are two possible ways of interpreting such behaviour (even without appeal to cognitively 'rich' conscious states such as "oh, yikes, a hawk! Better run!"). We might consider it an innate behaviour, i.e. a hardwired response to the hawk-shaped simulus. Alternatively, we might say that the behaviour arose from innate information, coded into mouse genes over generations of natural selection. Now, I'm wondering whether these two explanations really are distinct, and if so, what the difference is.

It seems to me that the latter is merely a 'cognitive' interpretation of the former explanation. Both agree that the mouse is exhibiting an automatic behaviour, caused by some form of simple stimulus-response mechanism. It's just that the latter explanation interprets this mechanism as a kind of information-processing device. It takes in sensory input, compares it against some innate hawk-shaped 'template' or 'search image', and outputs the instruction to engage in scurrying behaviour.

On the other hand, I'm not sure we want to say that whatever can be interpreted as an information processor therefore is one. For it seems a similar analysis would apply to mousetraps. (They detect the information that weight is being applied to the trigger, and output "instructions" to spring the trap.) But we presumably wouldn't really want to say that mousetraps are cognitive systems, would we?

Perhaps we could draw the line based on how much internal processing of the information really occurs. If there is a more or less direct connection between 'input' and 'output', as in the mousetrap, we can deny that any real processing of information has occured. If the mouse's scurrying behaviour was similarly direct, then we might deny that the cognitive interpretation applied, instead insisting that only the 'innate behaviour' description was appropriate. However, if we found that a fair bit of internal processing had to occur in order to identify the stimulus and match it up to the response, then we might say that the behaviour explanation is too superficial, and that it's more appropriate to opt for the cognitive explanation in such cases.

Does that sound plausible? Can you think of any alternative responses to this problem? (Any suggestions would be much appreciated!)

I'll finish up with a neat example of innateness that came up in class:
In normal populations, female sticklebacks are disposed to produce courtship responses to stimuli which carry the information ‘red below’. Isolation experiments show that this response pattern develops in females independently of any opportunities they have for learning that sexually mature male sticklebacks have red bellies. Mayr reports that in one stream system on the Olympic Peninsula, there is a population of jet black sticklebacks. The population evolved from red to black bellies about 8000 years ago, in response to local predatory pressures. For the last 8000 years, the Olympic females have been courted by and have mated with black males. Mayr reports the following remarkable fact: “when given a free choice between a black and a red-bellied male, (the black female) chose the red male five out of six times after 8000 years of ‘habituation’ to black males!” (Ernst Mayr 1974).

In other words, the Olympic sticklebacks retained innate information that hadn't been used in their lineage for 8000 years -- what a memory! (The 'innate behaviour' interpretation doesn't sound quite so impressive, for some reason.)

Update: Lorenz argues that only information (not behaviour) can be innate, on conceptual grounds. So I take it they aren't two distinct empirical theories after all. Rather, the claim is that the 'innate behaviour' explanation is simply incoherent. Behaviour always depends upon environmental contingencies. Genetic information is the only thing about an organism that is truly innate.

1 comment:

  1. I think it is VERY rare for things to happen in the brain of an animal in a particularly simplistic manner - the basic explinations like "It takes in sensory input, compares it against some innate hawk-shaped 'template' or 'search image', and outputs the instruction to engage in scurrying behaviour." there is all sorts of other things going on that eventually result in that reaction even if even the individual in question only percieves that simple logic.
    the same is true for learned and genetic information - it is ridiculously improbable ot have a gene or an experience that does exactly what you want i nthe simpilest way - what is likely is somthign that does basically what you want in a complex way


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