Hand preferences in Barbary macaques (Macaca sylvanus).

German Primate Center, Göttingen, Germany.
Laterality (Impact Factor: 1.13). 04/2008; 13(2):143-57. DOI: 10.1080/13576500701757532
Source: PubMed

ABSTRACT Nearly 90% of humans are right-handed, raising the question of the evolutionary origins of this trait. While lateralisation of certain actions appears to be widespread in vertebrates, the question of whether nonhuman primates exhibit hand preferences at the population level is often contested. We observed Barbary macaques (Macaca sylvanus) living in the outdoor enclosure "La Forêt des Singes" at Rocamadour, France, while performing simple unimanual and coordinated bimanual tasks. For the unimanual task, we recorded continuously which hand they used reaching for grains. For the coordinated bimanual tasks, a semi-transparent box and a tube baited with peanut butter were presented to the macaques and the hand used to open the box or reach into the tube, respectively, was recorded. We found no significant hand preference in any of the tasks at the population level, but found individual hand preferences, the extent of which varied among individuals. For the unimanual, but not the bimanual task, we found that the handedness index increased with age. Our results add to the growing body of evidence that monkeys do not show hand preference at the population level.

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    ABSTRACT: Background The present study aimed to determine and confront hand preference (hand chosen in priority to perform a manual dexterity task) and hand dominance (hand with best motor performance) in eight macaques (Macaca fascicularis) and in 20 human subjects (10 left-handers and 10 right-handers). Methods Four manual dexterity tests have been executed by the monkeys, over several weeks during learning and stable performance phases (in controlled body position): the modified Brinkman board, the reach and grasp drawer, the tube and the bimanual board tasks. Three behavioral tests, adapted versions from the monkeys tasks (modified Brinkman board, tube and bimanual board tasks), as well as a handedness questionnaire, have been conducted in human subjects. Results In monkeys, there was a large disparity across individuals and motor tasks. For hand dominance, two monkeys were rather right lateralized, three monkeys rather left lateralized, whereas in three monkeys, the different parameters measured were not consistent. For hand preference, none of the eight monkeys exhibited a homogeneous lateralization across the four motor tasks. Macaca fascicularis do not exhibit a clear hand preference. Furthermore, hand preference often changed with task repetition, both during training and plateau phases. For human subjects, the hand preference mostly followed the self-assessment of lateralization by the subjects and the questionnaire (in the latter, right-handers were more lateralized than left-handers), except a few discrepancies based on the tube task. There was no hand dominance in seven right-handers (the other three performed better with the right hand) and in four left-handers. Five left-handers showed left-hand dominance, whereas surprisingly, one left-hander performed better with the right hand. In the modified Brinkman board task, females performed better than males, right-handers better than left-handers. Conclusions The present study argues for a distinction between hand preference and hand dominance, especially in macaque monkeys.
    09/2013; 3(5):575-95. DOI:10.1002/brb3.160
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    ABSTRACT: In the past 20-25 years, there have been a number of studies published on handedness in nonhuman primates. The goal of these studies has been to evaluate whether monkeys and apes show patterns of hand preference that resemble the right-handedness found in the human species. The extant findings on handedness in nonhuman primates have revealed inconsistent evidence for population-level handedness within and between species. In this article, I discuss some of the methodological and statistical challenges to comparative studies of handedness in human and nonhuman primates. I further offer a framework for developing some consensus on evaluating the validity of different handedness measures and the characterization of individual hand preferences. © 2013 Wiley Periodicals, Inc. Dev Psychobiol.
    Developmental Psychobiology 09/2013; 55(6). DOI:10.1002/dev.21139 · 3.16 Impact Factor
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    ABSTRACT: This is the first study to examine hand preferences in Tonkean macaques on a bimanual task. One of our objectives was to continue the move toward greater task standardization, in order to facilitate comparisons between species and studies on handedness. The main aim was to test and determine task robustness, by varying intra-task complexity. To this end, we administered several different tasks to the subjects: two unimanual tasks (grasping task featuring items of different sizes) and three coordinated bimanual tasks (tube task involving different materials, weights, and diameters). Although we found no significant hand preference in either task at the group level, the macaques were more strongly lateralized for small items than for large ones in the unimanual grasping task. Moreover, the absence of a correlation between these two versions of the unimanual task confirmed the weakness of this grasping task for assessing handedness. Regarding the bimanual tube task, no difference was found between the three versions in either the direction or the strength of hand preference. Moreover, the highly correlated hand preferences between these three versions suggest that the tube task provides a more robust means of measuring manual preferences. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 11/2013; 152(3). DOI:10.1002/ajpa.22342 · 2.51 Impact Factor


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