Posture and laterality in the bushbaby (Galago senegalensis).

A colony of adult bushbabies was assessed for hand preference in order to determine what the proportion of preference for the left and right might be for the population and whether hand preference for individuals was reliable. 25 animals were tested in an apparatus demanding a vertical stance. The population bias was expressed in a distribution skewed toward a left-hand bias. With 16 animals available for retesting, the test-retest reliability coefficient was 0.651, significant at the 0.01 level. When 12 of the original subjects were tested in an apparatus demanding a quadrupedal stance, hand preference shifted to a bimodal distribution. Test-retest reliability was 0.864, significant at the 0.01 level. Significant correlations were not found between two types of test nor between the two retests. Neither sex nor length of laboratory residence served to predict hand preference. These results were discussed with the view that the postural adjustments required by a bipedal stance may have shaped the development of handedness in humans.