Association Cortex Size
The classical association cortical regions are larger in absolute terms in humans than in other primates,
and also larger relative to primary sensorimotor regions. In humans and in apes, the lower-order sensorimotor areas of the cortex are about the same absolute size (in surface area and volume). Human brains are much larger than those of apes, and the difference reflects the much greater absolute and relative size of the "association" cortex, including the classical prefrontal, posterior parietal, and temporal association regions.
Data come primarily from the work of Brodmann (1912) and Blinkov and Glezer (1968). See the recent summary in Preuss (2011).
Humans have much more association cortex, both in absolute amount and relative to the amount of primary sensory and motor cortex, than do apes or monkeys.
The association cortices provide the main neural substrate of the extreme cognitive and behavioral specializations of the human species.
The human brain: rewired and running hot., , Ann N Y Acad Sci, May, Volume 1225 Suppl, p.E182-91, (2011)
The Human Brain in Figures and Tables, , New York, (1968)
Neue Ergibnisse uber die vergleichende histologische Lokalisation der Grosshirnrinde mit besonderer Berucksichtigung des Stirnhirns, , Anat Anzeiger, Volume 41, p.157-216, (1912)