Can we measure brain efficiency? An empirical test with common marmosets (Callithrix jacchus)

Area of Science:

• Primate cognition
• Neuroscience
• Evolutionary biology

Background:

• Brain size correlates with cognitive performance, but the relationship is imperfect, suggesting variation in brain efficiency.
• Ecological and social pressures may constrain brain size while favoring enhanced cognitive abilities.
• Callitrichid monkeys, with relatively small brains, are hypothesized to possess high brain efficiency compared to related taxa like Cebus.

Purpose of the Study:

• To investigate if callitrichid monkeys exhibit cognitive performance exceeding expectations based on their brain size.
• To compare the relative cognitive efficiency of callitrichids with that of capuchin monkeys (Cebus).

Main Methods:

• Utilized the reversal learning paradigm, a reliable measure of cognitive performance across primate taxa.
• Assessed cognitive performance (transfer index) in 14 common marmosets (Callithrix jacchus) representing callitrichids.

Main Results:

• Marmosets demonstrated higher cognitive performance than predicted by their brain size.
• The relative cognitive performance of marmosets surpassed that of capuchin monkeys.

Conclusions:

• Callitrichid cognitive efficiency may be influenced by their cooperative breeding system.
• Shared care and provisioning behaviors might enhance cognitive and behavioral propensities in callitrichids.