NEOCORTEX SIZE AND BEHAVIORAL ECOLOGY IN PRIMATES

The neocortex is widely held to have been the focus of mammalian brain evolution, but what selection pressures explain the observed diversit y in its size and structure? Among primates, comparative studies sugge st that neocortical evolution is related to the cognitive demands of s ociality, and here I confirm that neocortex size and social group size are positively correlated once phylogenetic associations and overall brain size are taken into account. This association holds within haplo rhine but not strepsirhine primates. In addition, the neocortex is lar ger in diurnal than in nocturnal primates, and among diurnal haplorhin es its size is positively correlated with the degree of frugivory. The se ecological correlates reflect the diverse sensory-cognitive functio ns of the neocortex.