Hand Preferences for Bimanual Coordination in 77 Bonobos (Pan paniscus): Replication and Extension

Abstract

The literature on manual laterality in nonhuman primates provides inconsistent and inconclusive findings and is plagued by methodological issues (e.g., small samples, inconsistency in methods, inappropriate measures) and gaps. Few data are available on bonobos and these are only from small samples and for relatively simple tasks. We examined laterality in a large sample of bonobos for a complex task. We tested 48 bonobos from Lola Ya Bonobo sanctuary (DR Congo) in an extension of our previous study of 29 bonobos from 3 European zoos. We assessed hand preferences using the tube task, which involves bimanual coordination: one hand extracts food from a tube that is held by the other hand. This task is a good measure of laterality and it has been used in other studies. We recorded events (frequency) and independent bouts of food extraction. We found significant manual laterality, which was not influenced by the settings or rearing history. We observed little effect of sex and found an influence of age, with greater right hand use in adults. The laterality was marked, with strong preferences and most individuals being lateralized (when analyzing frequency). We found individual preferences, with no group-level bias, even when we combined the data from the sanctuary and the zoos to enlarge the sample to 77. These first data, for a complex task and based on a large sample, are consistent with previous findings in Int bonobos and in other nonhuman primate species for a variety of tasks. They suggest that, despite particular features in terms of proximity to humans, language and bipedalism, bonobos do not display a laterality that is more marked or more similar to human handedness compared to that of other nonhuman primate species.

Nut‐cracking behaviour in wild‐born, rehabilitated bonobos (Pan paniscus): a comprehensive study of hand‐preference, hand grips and efficiency

“…Similar findings have been made for other tool use actions in wild chimpanzees or captive capuchin monkeys [Westergaard et al, 1998;McGrew and Marchant, 1997b;McGrew et al, 1999;Londsdorf and Hopkins, 2005]. When bonobos are faced with artificial complex bimanual manipulative tasks, they show strong laterality at an individual-level but not at a group-level or population-level [Chapelain et al, 2011;Hopkins et al 2011;Bardo et al, 2015]. However, apart from these few studies, there are no published data on laterality during a natural complex bimanual task performance in bonobos.…”

“…Hand-preference or laterality was recorded for bouts to ensure independence of data points [e.g., McGrew and Marchant, 1997;Humle and Matsuzawa, 2009;Chapelain et al, 2011]. Only individuals for whom a minimum of 10 bouts or more were recorded were included in the analysis [Humle and Matsuzawa, 2009].…”

“…We further tested the probability of success for the two proportions (R vs. L) in a Bernoulli trial (significance set at p= 0.05). We calculated a handedness index (HI) score ranging from -1 to +1 for each individual based on the total number of bouts: HI=(R-L)/(R+L) [Humle and Matsuzawa, 2009;Chapelain et al, 2011]. Negative values indicate a left hand bias and positive values indicate a right-hand bias.…”

“…spontaneous actions like reaching or feeding) in relatively small samples (2-10 individuals) [De Vleeschouwer et al, 1995;Hopkins and de Waal, 1995;Ingmanson, 1996]. Although studies of more complex bimanual tasks found stronger individual hand preferences, no individuals were exclusively right-or left-handed [e.g., Chapelain et al, 2011;Hopkins et al, 2011;Bardo et al, 2015]. In contrast to this previous work, the individual bonobos in this study were exclusively right-or left-handed and there was an overall significant right-hand bias at the group-level during nut-cracking.…”

Laterality of Grooming and Tool Use in a Group of Captive Bonobos (Pan paniscus)

“…Tool use is closely scrutinized given its cultural variation among wild chimpanzees [Whiten et al, 1999] and has also been invoked as a potential selective pressure for human handedness [Kimura, 1979]. In contrast to their sister species, wild bonobos are not known to use tools in food-processing tasks [Furuichi et al, 2011;Koops et al, 2015]; however, their capacity to use tools in captivity is well documented [Gruber et al, 2010;Chapelain et al, 2011;Boose et al, 2013;Bardo et al, 2015]. Thus, studies of tool use laterality in bonobos have focused on captive individuals.…”