Tuesday, February 06, 2007

Fish brains can perform transitive analysis

Yesterday's post on fish brains switching their sexuality reminds me of another bit of work on fish that I have been meaning to mention:

Transitive inference involves using known relationships to deduce unknown ones (for example, using A > B and B > C to infer A > C), and is thus essential to logical reasoning. First described as a developmental milestone in children, Transitive inference has since been reported in nonhuman primates, rats, and birds.

In many social species (whether they are teleost fish or mammals) a behavioral hierarchy establishes itself which regulates who gets first access to food and mates. A reason that transitive behavior would evolve is that it saves a lot of energy if you don't have to go into head on competition with every other male you meet to determine who is on top. If you can see competitions between other males and learn who wins over who, you learn who is safer to hang out with. This rationale should be true for both territorial and non-territorial species that maintain social hierarchies, so you might not be surprised to find it wherever such hierarchies are established.

Experiments in Fernald's lab at Stanford now show that male fish (Astatotilapia burtoni) can successfully make inferences on a hierarchy implied by pairwise fights between rival males. These fish learned the implied hierarchy vicariously (as 'bystanders'), by watching fights between rivals arranged around them in separate tank units.

What this says about fish brains is that they can perform a transitive analysis, just as they can do many other quite amazing feats of analysis. It does not say anything about the kind of experienced awareness or consciousness they have. It could a process as automatic and rote as the operant conditioning which trains them to avoid stimuli in the past have resulted in dangerous or unpleasant experiences.

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