CZAAWE Resource Article

Grooming, social rank and ‘optimism’ in tufted capuchin monkeys: a study of judgement bias
Publication Type 
Journal Article
Year of publication 
2016
Publication/Journal 
Animal Behaviour
ISBN 
0003-3472
Abstract 
Studying the emotional consequences of social behaviour in nonverbal animals require methods to access their emotional state. One such method is provided by cognitive bias tests. We applied a judgement bias test to tufted capuchin monkeys, Sapajus sp., to evaluate (1) whether receiving grooming was associated with a short-term increase in ‘optimism’ (that is, a positive bias in the interpretation of ambiguous stimuli) and (2) whether interindividual differences in ‘optimism’ were related to dominance rank or overall rates of social and nonsocial behaviour. Receiving grooming had no detectable immediate consequences, but increased ‘optimism’ was observed in dominant monkeys and in monkeys that received overall larger quantities of grooming. These results provide only partial support for the hypothesis that a system of emotional bookkeeping underlies the capacity of group-living animals to reciprocate cooperative interactions.