Within- and between-task consistency in hand use as a means of characterizing hand preferences in captive chimpanzees (Pan troglodytes).

Hopkins²,

Misiura

et al. 2016

Neuropsychologia

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Increases brain size has been hypothesized to be inversely associated with the expression of behavioral and brain asymmetries within and between species. We tested this hypothesis by analyzing the relation between asymmetries in the planum temporale (PT) and different measures of the corpus callosum (CC) including surface area, streamline count as measured from diffusion tensor imaging, fractional anisotropy values and the ratio in the number of fibers to surface area in a sample of chimpanzees. We found that chimpanzees with larger PT asymmetries in absolute terms had smaller CC surface areas, fewer streamlines and a smaller ratio of fibers to surface area. These results were largely specific to male but not female chimpanzees. Our results partially support the hypothesis that brain asymmetries are linked to variation in corpus callosum morphology, although these associations may be sex-dependent.

Section: Methodsmentioning

confidence: 99%

Sex differences in the relationship between planum temporale asymmetry and corpus callosum morphology in chimpanzees (Pan troglodytes): A combined MRI and DTI analysis

Hopkins²,

Misiura

et al. 2016

Neuropsychologia

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“…Whether this is a problem in the existing nonhuman primate handedness literature is unclear because consistency in hand use across different test sessions or observation periods is seldom reported (Hopkins et al, in press). However, two recent studies on handedness for the TUBE task in chimpanzees collected hand use data in 4 separate test sessions (Hopkins et al, in press; Llorente et al, 2010).…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

“…However, two recent studies on handedness for the TUBE task in chimpanzees collected hand use data in 4 separate test sessions (Hopkins et al, in press; Llorente et al, 2010). HI scores were calculated for each test session and the chimpanzees’ handedness was classified based on their consistency in hand use across tests.…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

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Independence of data points in the measurement of hand preferences in primates: Statistical problem or urban myth?

American J Phys Anthropol

2013

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Lack of independence of data points or the pooling fallacy has been suggested as a potential problem in the study of handedness in nonhuman primates, particularly as it relates to whether hand use responses should be recorded as individual events or bouts of activity. Here, I argue that there is no evidence that the concept of statistical independence of data points or the pooling fallacy is a problem in the evaluation of population-level handedness in previous studies in nonhuman primates. I further argue these statistical concepts have been misapplied to the characterization of individual hand preferences. Finally, I argue that recording hand use responses as bouts rather than events has no significant effect on reports of hand use in nonhuman primates and, in fact, may unintentionally bias hand use toward the null hypothesis. Several suggestions for improvement in the measurement and statistical determination of individual handedness are offered in the paper.

“…Alternatively, others have suggested that increasingly lateralization was associated with selection for increasingly sophisticated communication skills, particularly in the domain of gestural communication [74]. Evidence in support of this theory largely come from data showing that hand preferences, and specifically right-handedness, is more pronounced for gestural communication when compared to hand use for non-communicative actions such as simple reaching or coordinated bimanual actions in human infants, apes and some monkey species [75–78]. At face value, the evidence presented here supports the evolutionary model of the role of tool use, and more generally object manipulation, on potential changes in brain organization and asymmetry [79–81]; however, we did not directly test this framework against lateralization for manual gestures and, to be fair, there is some evidence that chimpanzees that prefer to gesture with their right hand showed larger leftward asymmetries in the IFG compared to non-right-handed individuals [82].…”

Section: Discussionmentioning

confidence: 99%

Motor skill for tool-use is associated with asymmetries in Broca’s area and the motor hand area of the precentral gyrus in chimpanzees ( Pan troglodytes )

Behavioural Brain Research

Meguerditchian

Coulon

et al. 2017

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Among nonhuman primates, chimpanzees are well known for their sophistication and diversity of tool use in both captivity and the wild. The evolution of tool manufacture and use has been proposed as a driving mechanism for the development of increasing brain size, complex cognition and motor skills, as well as the population-level handedness observed in modern humans. Notwithstanding, our understanding of the neurological correlates of tool use in chimpanzees and other primates remains poorly understood. Here, we assessed the hand preference and performance skill of chimpanzees on a tool use task and correlated these data with measures of neuroanatomical asymmetries in the inferior frontal gyrus (IFG) and the pli-de-passage fronto-parietal moyen (PPFM). The IFG is the homolog to Broca’s area in the chimpanzee brain and the PPFM is a buried gyrus that connects the pre- and post-central gyri and corresponds to the motor-hand area of the precentral gyrus. We found that chimpanzees that performed the task better with their right compared to left hand showed greater leftward asymmetries in the IFG and PPFM. This association between hand performance and PPFM asymmetry was particularly robust for right-handed individuals. Based on these findings, we propose that the evolution of tool use was associated with increased left hemisphere specialization for motor skill. We further suggest that lateralization in motor planning, rather than hand preference per se, was selected for with increasing tool manufacture and use in Hominid evolution.