Does target animacy influence manual laterality of monkeys? First answer from northern pig-tailed macaques (Macaca leonina)

Abstract

The evolutionary origin of human right-handedness remains unclear. Many factors such as emotion and tool use have been implicated in primate handedness evolution. With regard to emotional lateralization, most related research focuses on facial asymmetry and behavioral laterality under the non-social context, whereas few studies investigate social laterality. This study, for the first time, investigates the effect of target animacy on hand preference in Old World monkeys, compares our findings with previous related studies in great apes and humans, and aids in filling the knowledge gap on primate handedness evolution. Nine captive northern pig-tailed macaques (Macaca leonina) were chosen as focal subjects in this study. There was no group-level handedness for both animate and inanimate targets. No significant interaction was found between lateral hand use and target animacy. Left-hand use was more frequent than right-hand use for animate targets, whereas right-hand use was more frequent than left-hand use for inanimate targets, both of which demonstrate no significant level. On the whole, northern pig-tailed macaques showed a similar tendency as that in great apes and humans. Regarding handedness linked with emotive stimuli, it is likely that Old World monkeys, great apes and humans evolved from a common ancestor.

How Target Animacy Affects Manual Laterality in Hylobatidae: The First Evidence in Northern White-Cheeked Gibbons (Nomascus leucogenys)

“…With regard to inanimate targets, northern white-cheeked gibbons did not show significant differences in bilateral hand use, which was concordant with all related findings in monkeys [e.g., M. leonina: Zhao et al, 2015;Rhinopithecus roxellana: Zhao et al, 2016], whereas great apes and humans displayed group-level right handedness [e.g., G. gorilla: Forrester et al, 2011;P. troglodytes: Forrester et al, 2012;H.…”

“…Current evidence shows that some primates prefer the use of the right hand during unimanual reaching for inanimate targets in comparison with animate targets [e.g., Gorilla gorilla: Forrester et al, 2011;Pan troglodytes: Forrester et al, 2012;Homo sapiens: Forrester et al, 2013;Macaca leonina: Zhao et al, 2015], which conforms to expectations of the tool use theory wherein tool use plays a major role during the appearance of language syntax while original manipulative behavior was dominated by the left hemisphere [Greenfield, 1991;Corballis, 2002]. Meanwhile, this evidence indicates the early categorical neural distinction between animate targets that require social handling and inanimate targets that require functional handling among humans, great apes, and Old World monkeys [Forrester et al, 2011[Forrester et al, , 2012[Forrester et al, , 2013Zhao et al, 2015Zhao et al, , 2016.…”

“…Manual laterality at the group level was measured by a χ 2 goodnessof-fit test [Hopkins, 1999, Zhao et al, 2012. For the effect of animacy on hand preference, we used the 2 (inanimate/animate targets) × 2 (left/right hands) repeated measures analysis of variance as well as paired-sample t tests based on proportion data (dividing the frequency of bilat- eral hand use by total frequencies) and rate data (dividing the frequency of bilateral hand use by total observation minutes), respectively [Forrester et al, 2011[Forrester et al, , 2012Zhao et al, 2015Zhao et al, , 2016. We used SPSS 21.0 for all statistical analyses.…”

“…From March to June 2016, we used a camera (SONY HDR-PJ390E) to collect twenty 10-min observation sessions for each individual when the gibbons made spontaneous activities (e.g., eating, moving, social interactions) via the method of focal individual sampling [Quaresmini et al, 2014;Zhao et al, 2015Zhao et al, , 2016. A camera was angled to include the area surrounding the focal subject during the data collection period.…”

“…Based on the research background above, this study explores for the first time how target animacy impacts on manual laterality of one Hylobatidae species, northern white-cheeked gibbons (Nomascus leucogenys), thus helping to further our understanding of the evolution of primate emotional lateralization. For inanimate targets, considering the reported pattern in monkeys, great apes, and humans [Forrester et al, 2011[Forrester et al, , 2012[Forrester et al, , 2013Zhao et al, 2015Zhao et al, , 2016, it is hypothesized that N. leucogenys would use the right hand more frequently than the left hand for inanimate targets. Furthermore, current findings suggest that the right hemisphere is more responsible for emotive stimuli based on primate lateralization research concerning facial expression [Lindell, 2013;Quaresmini et al, 2014].…”