Personality and social environment predict cognitive performance in common marmosets (Callithrix jacchus)

Abstract

Consistent inter-individual variation in cognition has been increasingly explored in recent years in terms of its patterns, causes and consequences. One of its possible causes are consistent inter-individual differences in behaviour, also referred to as animal personalities, which are shaped by both the physical and the social environment. The latter is particularly relevant for group-living species like common marmosets (Callithrix jacchus), apt learners that display substantial variation in both their personality and cognitive performance, yet no study to date has interlinked these with marmosets' social environment. Here we investigated (i) consistency of learning speed, and (ii) whether the PCA-derived personality traits Exploration-Avoidance and Boldness-Shyness as well as the social environment (i.e., family group membership) are linked with marmosets' speed of learning. We tested 22 individuals in series of personality and learning-focused cognitive tests, including simple motor tasks and discrimination learning tasks. We found that these marmosets showed significant inter-individual consistency in learning across the different tasks, and that females learned faster than males. Further, bolder individuals, and particularly those belonging to certain family groups, learned faster. These findings indicate that both personality and social environment affect learning speed in marmosets and could be important factors driving individual variation in cognition.

Figure 1

Sex differences in Overall Learning Speed (Z-score). ‘Overall Learning Speed (Z-score)’ signifies summed up values for total time taken to reach criterion across the different cognitive tasks, after a standardization, from all individuals. Low values on axis represent faster learning speed, whereas higher values represent slower learning speed. Box-plot limits indicate 25th and 75th percentiles; whiskers extend 1.5 times the interquartile range, dots indicate outliers.

Figure 2

Interaction effect of Boldness-Shyness and Group Membership on Overall Learning Speed (Z-score). ‘Overall Learning Speed (Z-score)’ signifies summed up values for total time taken to reach criterion across the different cognitive tasks, after a standardization. Low values on ‘Overall Learning Speed (Z-score)’ axis represent faster learning speed, whereas higher values represent slower learning speed. Low values on the PCA-obtained component Boldness-Shyness represent bolder individuals, whereas higher values represent shyer individuals. Different family groups are depicted in different colours (Pooh = blue; Sparrow = green; Ginevra = orange; Veli = purple; Kiri = yellow). Black line indicates overall fit line. Every point signifies an individual.