Revisiting the cognitive buffer hypothesis for the evolution of large brains

Abstract

Why have some animals evolved large brains despite substantial energetic and developmental costs? A classic answer is that a large brain facilitates the construction of behavioural responses to unusual, novel or complex socioecological challenges. This buffer effect should increase survival rates and favour a longer reproductive life, thereby compensating for the costs of delayed reproduction. Although still limited, evidence in birds and mammals is accumulating that a large brain facilitates the construction of novel and altered behavioural patterns and that this ability helps dealing with new ecological challenges more successfully, supporting the cognitive-buffer interpretation of the evolution of large brains.

Figure 1

Schematic representation of the CB hypothesis (see text for details; modified from Ricklefs & Wikelski 2002).

Figure 2

Framework to integrate the CB hypothesis into a more general life-history-based theory on brain evolution. The positive and negative effects are represented by the solid and dashed lines, respectively. 1, CB hypothesis; 2, delayed maturation hypothesis; 3, physiological regulator hypothesis; 4, growth regulation hypothesis; 5, neuronal investment hypothesis; 6, maturational constraints hypothesis; 7, social intelligence hypothesis.