Baseline cortisol levels and social behavior differ as a function of handedness in marmosets (Callithrix jacchus)

Abstract

Population hand preferences are rare in nonhuman primates, but individual hand preferences are consistent over a lifetime and considered to reflect an individual's preference to use a particular hemisphere when engaged in a specific task. Previous findings in marmosets have indicated that left‐handed individuals tend to be more fearful than their right‐handed counterparts. Based on these findings, we tested the hypotheses that left‐handed marmosets are (a) more reactive to a social stressor and (b) are slower than right‐handed marmosets in acquiring a reversal learning task. We examined the hand preference of 27 male and female marmosets (ages of 4–7 years old) previously tested in a social separation task and a reversal learning task. Hand preference was determined via a simple reaching task. In the social separation task, monkeys were separated from their partner and the colony for a single 7‐hr session. Urinary cortisol levels and behavior were assessed at baseline, during the separation and 24 hr postseparation. Hand preferences were equally distributed between left (n = 10), right‐handed (n = 10), and ambidextrous (n = 7) individuals. The separation phase was associated with an increase in cortisol levels and behavioral changes that were similar across handedness groups. However, cortisol levels at baseline were positively correlated with right‐handedness, and this relationship was stronger in females than in males. In addition, the occurrence of social behaviors (pre‐ and postseparation) was positively correlated with right‐handedness in both sexes. Baseline cortisol levels did not correlate significantly with social behavior. Acquisition of the reversals was poorer in females than males but did not differ as a function of handedness. We conclude that (a) both stress reactivity and cognitive flexibility are similar across handedness groups and (b) left‐handers exhibit less social behavior and have lower basal cortisol levels than ambidextrous and right‐handed subjects. The underlying causes for these differences remain to be established.

Age, but not hand preference, is related to personality traits in common marmosets (Callithrix jacchus)

“…In terms of hand preference, 50% of individuals were left-handed, 25% right-handed and 25% ambilateral. As in other studies on hand use in marmosets [ 49 , 51 – 53 ], we did not detect any population-level bias in hand preference. The individual hand preference was, however, highly consistent (across the time span of two years), but neither strength nor direction of hand preference were explained by individual's sex or age—a general pattern commonly reported for marmosets [ 51 – 53 , 55 ].…”

“…Across studies, right-handed marmosets exhibited more explorative, active, approach-prone and less fearful behaviours than the left-handed marmosets (reviewed in [ 30 ]). Specifically, right-handed marmosets touched more objects, were faster to enter a novel room or to approach novel food [ 46 ], emitted more vocalizations when confronted with novel food [ 57 ], reacted to predator vocalizations with less freezing behaviour [ 56 ], and exhibited more social behaviours [ 53 ]. However, none of the mentioned studies directly tested the relationship between hand preference and personality measured as repeated behavioural reactions, on a broader construct level.…”

Differential Ageing of the Brain Hemispheres: Evidence from a Longitudinal Study of Hand Preferences in Common Marmosets

“…The gradual decline in the strength of left-hand preference with age could also be associated with broader behavioural differences between left-handed and right-handed marmosets. Left-and right-handed marmosets differ in social behaviour: right-handed marmosets display higher levels of social interaction [33,52]. In fact, long-term records of behaviour of marmosets in our colony revealed that right-handed marmosets were more aggressive than left-handed marmosets, with the latter being recipients of more aggression and, hence, suffering more stress [53].…”

Hand preference predicts behavioral responses to threats in Barbary macaques

“…In common marmosets, left-handed individuals have more prolonged elevated cortisol levels, possibly indicating that they are more reactive to stress than right-handed individuals (Rogers, 2009). However, a different study reported that the basal cortisol of left-handed common marmosets was lower than that of right-handed individuals and that there is no difference in reactivity between left- and right-handed individuals (Vaughan et al, 2019). In Bonobos ( Pan paniscus ), no relationship between handedness and reactivity was found when investigating self-directed behavior and performance in cognitive tasks (Laméris et al, 2022).…”