Re-evaluating the link between brain size and behavioural ecology in primates

Area of Science:

• Evolutionary biology
• Comparative psychology
• Primatology

Background:

• Relative brain size is linked to behavioral and ecological factors, but findings vary across taxa.
• Primate studies conflict on whether social or ecological influences on brain size are more critical.

Purpose of the Study:

• To comprehensively re-examine correlates of primate brain size.
• To test the Social Brain Hypothesis by assessing the influence of social group size versus ecological variables.

Main Methods:

• Utilized two large comparative primate datasets.
• Employed phylogenetic comparative methods for analysis.
• Matched species composition and predictor variables across datasets.

Main Results:

• Found associations between primate brain size and ecological variables (home range, diet, activity period).
• Observed little evidence for a correlation between brain size and social group size.
• Detected instability in results across datasets, even when controlled.

Conclusions:

• Ecological factors, not social group size, appear more consistently associated with primate brain size.
• The instability of findings raises doubts about inferring cognitive selection pressures from behavioral correlates of brain size.
• Challenges the empirical basis of the Social Brain Hypothesis and highlights methodological difficulties.