Brain and Behavior


Variation Within a Species

hermaphroditic fish
domestic cats
crayfish aggression

Alzheimer's and other Pathologies

The Question of Gender

The Question of Sexuality



Can we relate this thought process to humans?

All of these examples of individual variation within a species are interesting in and of themselves, right? We've seen that:

  • certain types of fish can change sex according to the social group around them;
  • wild cats and domestic cats have specific structural and functional brain differences (and, of course, behavioral differences);
  • and a change in an crayfish' social status has an effect on how the brain uses a neurochemical.

How does this connect with humans? Can we make any inferences about our brains and behavior using the knowledge we now have about other animals?

For example, consider this: a few human individuals are in a park. Individual A is participating aggressively in a wrestling match with a competitor. Individual B is coddling an infant in its lap, fearing the potential for harm that Individual A is enduring. What could we say about these two individuals, without knowing anything about them than our observations? Do the behavior differences that we observe indicate anything about the structure or function of their brain? Of course not-- we cannot make a rash judgement from simply one observation. HOWEVER . . . what if I told you that Individual A was a man and Individual B was a woman? Would you then feel comfortable making a hypothesis about potential differences between the two individuals?

Here's another example: Patient A is has a fully functional ability to communicate. Patient B has no memory of past or understanding of the present. Patient A is able to construct full sentences and tell us what was for dinner yesterday. Patient B finds it difficult to identify himself. Can you tell me anything about similarities or differences of these patients' brains? No? Well . . .what if I told you that Patient A is 30 years old and Patient B is 90 years old? Does that enable you to make guesses as to the basis for these individual differences?

Do you see where I'm going with this? Even in humans there are definite behavior differences between individuals that may be correlated with differences in the brain. Let's consider some possibilities:

Alzheimer's and Diseases of Aging

Gender and Sexual Orientation