Article

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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Available from: Julia Fischer, Nov 20, 2014
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    • "For the reach and grasp drawer task (in monkeys only), the preferred hand is the hand grasping the reward (manipulative role) while the other hand, the postural one, holds the drawer. For these three tasks (bimanual Brinkman board task, reach and grasp drawer task, tube task), we computed the HI (Westergaard et al. 1997; Spinozzi et al. 1998; Hopkins et al. 2004; Schmitt et al. 2008), defined as follows: the number of trials the right hand (R) was used as preferred hand minus the number of times the left hand (L) was used as preferred hand, divided by the total number of trials: HI ¼ ðR – LÞ=ðR + LÞ Consequently, a negative HI reflects a left bias whereas a positive HI reflects a right bias. The HI (lateralization) ranges between +1 (strongly right-handed) and À1 (strongly left-handed). "
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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.
    Brain and Behavior 09/2013; 3(5):575-95. DOI:10.1002/brb3.160
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    • "events) of left and right hand use (Vauclair et al., 2005; Lilak and Phillips, 2007; Meunier and Vauclair, 2007; Bennett et al., 2008; Llorente et al., 2010; Hopkins et al., 2011; Meguerditchian et al., 2012). In contrast, others have suggested that each of the hand use responses presented above is not independent of the other and therefore represents a " lack of data independence " (Hopkins et al., 2001; Schweitzer et al., 2007; Schmitt et al., 2008;Chapelain and Hogervorst, 2009; Chapelain et al., 2011; Zhao et al., 2012). The argument is that because the first hand use event predicts or is correlated with subsequent responses, the data are not independent of each other. "
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    ABSTRACT: 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 article. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 05/2013; 151(1). DOI:10.1002/ajpa.22248 · 2.51 Impact Factor
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    • "The mean HI score based on frequency data for 10 nonhuman primate species that has been tested on the tube task * indicates significant population-level handedness based on combined published data from each species. Handedness data for each species came from the following sources: Great apes from Hopkins et al. (2011) and Llorente et al. (2011), rhesus monkeys from Bennett et al (2008), Barbary macaques from Schmitt et al. (2008), baboons from Vauclair et al. (2005), De Brazza monkeys from Schweitzer et al. (2007), and capuchin monkeys from Lilak and Phillips (2008), Meunier and Vauclair (2007) and Spinozzi et al. (1998). Samples sizes for each species were: chimpanzees (n = 536), bonobos (n = 118), gorillas (n = 76), orangutans (n = 44), De Brazza (n =12), rhesus (n =74), Barbary (n = 28), baboon (n = 104) and capuchins (n = 54). "
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    ABSTRACT: Handedness is a defining feature of human manual skill and understanding the origin of manual specialization remains a central topic of inquiry in anthropology and other sciences. In this study, we examined hand preference in a sample of wild primates on a task that requires bimanual coordinated actions (tube task) that has been widely used in captive primates. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is an arboreal Old World monkey species that is endemic to China, and 24 adult individuals from the Qinling Mountains of China were included for the analysis of hand preference in the tube task. All subjects showed strong individual hand preferences and significant group-level left-handedness was found. There were no significant differences between males and females for either direction or strength of hand preference. Strength of hand preferences of adults was significantly greater than juveniles. Use of the index finger to extract the food was the dominant extractive-act. Our findings represent the first evidence of population-level left-handedness in wild Old World monkeys and broaden our knowledge on evaluating primate hand preference via experimental manipulation in natural conditions.
    American Journal of Physical Anthropology 05/2012; 148(1):36-44. DOI:10.1002/ajpa.22038 · 2.51 Impact Factor
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