Source Paper
Evan L. MacLean, Brian Hare, Charles L. Nunn, Elsa Addessi, Federica Amici et al.
Proceedings of the National Academy of Sciences • 2014
Significance Although scientists have identified surprising cognitive flexibility in animals and potentially unique features of human psychology, we know less about the selective forces that favor cognitive evolution, or the proximate biological mechanisms underlying this process. We tested 36 species in two problem-solving tasks measuring self-control and evaluated the leading hypotheses regarding how and why cognition evolves. Across species, differences in absolute (not relative) brain volume best predicted performance on these tasks. Within primates, dietary breadth also predicted cognitive performance, whereas social group size did not. These results suggest that increases in absolute brain size provided the biological foundation for evolutionary increases in self-control, and implicate species differences in feeding ecology as a potential selective pressure favoring these skills.
Objective: Quantitatively compare cognitive performance across 567 individuals representing 36 species on two problem-solving tasks measuring self-control and executive function to test evolutionary hypotheses about cognitive evolution
Recruited 567 individuals representing 36 species for cognitive testing
Note: Multi-site collaborative study involving researchers from multiple institutions across different countries
“quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control”
Administered two problem-solving tasks measuring self-control and executive function to all subjects
Note: Tasks designed to measure inhibitory control and self-control across diverse species
“two problem-solving tasks measuring self-control”
Measured absolute brain volume and brain volume controlling for body mass for each species
Note: Data used to test proximate evolutionary explanations for cognitive differences
“absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity”
Collected dietary breadth and social group size data for primate species
Note: Data used to test ultimate evolutionary explanations for cognitive differences within primates
“Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control”
Conducted phylogenetic analysis to evaluate relationships between brain volume, dietary breadth, and cognitive performance
Note: Analysis tested leading hypotheses regarding how and why cognition evolves
“Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass”
Study includes primates and non-primates; dietary breadth and social group size measured within primates