By relating proxies of cognitive ability to brain size, numerous studies have found positive relationships between brain size and behaviors believed to be connected to cognitive ability.
The limited explanatory power of the brain-migration association is not surprising considering the variety of environmental factors that may influence brain size and migratory behavior.
Passerine birds are ideal for our study because they show substantial variation in both brain size and migratory behavior [18], [44].
Previous analyses have shown that brain size and structure are associated with ecology and behavior [ 16, 21- 23], suggesting that, as with other morphological traits, brain size and structure are also highly variable within Tanganyikan cichlids.
Since then, Raine, a criminologist and psychologist at the University of Pennsylvania, and the author of "The Anatomy of Violence," has become an expert on L.R.H.R. and other possible biological markers of antisocial behavior, such as brain size and neurotransmitter levels.
In total, 20 genes were found to be necessary for proper brain size and shape, with subsets also affecting eye development, axon tract organization, movement behaviors and muscle formation.
Indeed, the Machiavellian Intelligence hypothesis argues that an ability to detect (and counter) deceptive behaviors based on cognitive mechanisms has been a major factor underpinning the evolution of large brain size and advanced cognitive abilities among primates [Byrne & Whiten, 1990, 1992].
No interactions between brain size and gender were found.
