reflects a left-hand bias (Hopkins, 1995). Absolute ... regardless of left or right hand (Hopkins, 1995). ... held in Bucknell University (Caitlin Samuel, personal.
Talk To The Hand: Hamadryas Baboons (Papio hamadryas) Hand Preference in Gestural Communication Raymond Vagell Animal Behavior and Conservation Program, Department of Psychology, Hunter College (CUNY)
RESULTS
This preliminary study sought to elucidate whether hamadryas baboons (Papio hamadryas) at the Prospect Park Zoo (WCS) in Brooklyn, New York exhibit hand preference in unimanual gestural communication.
Hand Slap Handedness Index (HI) in P. hamadryas at Prospect Park Zoo
Hand slap: A quick and repetitive rubbing or slapping of the hand on the ground. Sign of aggression. Muzzle wipe: Self-directed spontaneous behavior where an individual touches its own muzzle. Sign of stress. Because muzzle is in the middle of the face, we expect that there is no positional bias in hand preference. However, we do expect a hand preference in hand slapping.
Subjects
INTRODUCTION
DISCUSSION 42.9% of P. hamadryas at the Prospect Park Zoo exhibit a right-hand preference for hand slap. Rebecca (None) Kaia (None) Binti Matara Kobo Simen Bole
0.1 0.9
-1 1 1
-1
-0.5
0
0.5
1
Hand Slap (HI)
Figure 1: Hand slap HI for all P. hamadryas at the Prospect Park Zoo (X2 (1, N = 5) = 17.04, p < 0.001)
Muzzle Wipe Handedness Index (HI) in P. hamadryas at Prospect Park Zoo Rebecca Kaia Binti Matara Kobo Simen Bole
0.1 0.3
1. There is a hand preference for hand slap. Subjects
0.2 -0.1
0.4 0.4
METHODS
-1
Conducted between April 17th & May 4th, 2013. Observations were done at varying times between 12 PM to 5 PM using all occurrence sampling.
The absence of hand slapping in 2 baboons could be cultural. These females (Rebecca and Kaia) were known to not hand slap where they were previously held in Bucknell University (Caitlin Samuel, personal communication, 2014). Hand slapping could have also occurred when out of sight. 71.4% of P. hamadryas at the Prospect Park Zoo exhibit a right-hand preference for muzzle wipe.
Hypotheses:
2. There is no hand preference for muzzle wipe.
Hand slap is the most lateralized: 3 baboons with maximum ABS-HI of 1.0 & 1 baboon with ABS-HI of 0.9.
-0.5
0
0.5
Muzzle wipe is the least lateralized: 4 baboons exhibited right-hand preference with the maximum ABS-HI of 0.4. Although most baboons have a right-hand preference for muzzle wipe, the ABS-HI indicates that the strength is low.
CONCLUSIONS 1
Muzzle Wipe HI
Figure 2: Muzzle wipe HI for all P. hamadryas at the Prospect Park Zoo (X2 (1, N = 7) = 10.50, p < 0.05)
Results are consistent with previous studies on another baboon species, olive baboons (Papio anubis) (Vauclair et al., 2005; Meguerditchian & Vauclair, 2006; Meguerditchian & Vauclair, 2009). Results from this pilot study can contribute to the study of nonhuman primate handedness, as well as the evolution of human language.
(X2)
Handedness Index (HI) & chi-squared tests for hand preference were tabulated for each subject. HI = (R-L) ÷ (R+L); -1.0 ≥ HI ≤ 1.0
REFERENCES
HI was used to characterize each subject’s hand preference based on a continuum of highly left-handed to highly right-handed.
Hopkins, W.D. 1995. Hand Preferences for a Coordinated Bimanual Task in 110 Chimpanzees (Pan troglodytes): Cross-Sectional Analysis. Journal of Comparative Psychology 109(3): 291 - 297.
Positive HI reflects a right-hand bias; negative HI reflects a left-hand bias (Hopkins, 1995).
Hopkins, W.D. 2013. Independence of Data Points in the Measurement of Hand Preferences in Primates: Statistical Problem or Urban Myth? American Journal of Physical Anthropology 151(1):151-7.
Absolute value of handedness index (ABS-HI) reflects the strength of a subject’s hand preference regardless of left or right hand (Hopkins, 1995). Considered no left- or right-hand preference if -0.2 > HI < 0.2 (Hopkins, 2013).
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Illustration 1: (From left to right) (Top) Simen, Bole & Kobo. (Bottom) Matara, Binti, Kaia & Rebecca.
ACKNOWLEDGEMENT I would like to thank Dr. Scott Silver for his help in this study. Thanks to Terry Webb, the Prospect Park Zoo, as well as the hamadryas baboon troop for making this study possible.
Meguerditchian, A & Vauclair, J. 2006. Baboons communicate with their right hand. Behavioural Brain Research 171: 170 - 174. Meguerditchian, A & Vauclair, J. 2009. Contrast of hand preferences between communicative gestures and non-communicative actions in baboons: Implications for the origins of hemispheric specialization for language. Brain & Language 108: 167 - 174. Vauclair, J. Meguerditchian, A & Hopkins, W.D. 2005. Hand preferences for unimanual and coordinated bimanual tasks in baboons (Papio anubis). Brain Res Cogn Brain Res 25(1): 210 - 216.
