The g factor in non-human animals.

Animals possess the attributes we label as 'intelligent' in humans. 'Insight' and 'reasoning' have been demonstrated in chimpanzees, monkeys, racoons, rats, mice, ravens and pigeons. In the rat, the animal species best characterized psychologically and neuroanatomically, reasoning ability correlates with other cognitive capacities and brain size. Other learning task paradigms tested on mice and rats have confirmed consistent individual differences, indicated a neuroanatomical network for learning, and shown the presence of genetic influences for cognitive ability. Animals offer an opportunity to test ideas about intelligence that cannot be performed on humans. Methylazoxymethanol (MAM) administered prenatally can arrest cortical cell division and produce a 'mentally retarded' microcephalic rat. This intellectual deficiency can be ameliorated by postnatal induction of dendritic arborization and synapse formation with naltrexone, suggesting the relevance of neuronal and synapse number for behavioural variation in rat g. Inbred mice lines differ in brain size and behaviour, permitting, through the use of recombinant inbred strains, the determination of genetic loci with quantitative effects on structure and function. Lastly, genetic contributions to g can be directly tested by modifying gene expression and determining the anatomical, physiological, and behavioural benefits.