TABLE 1.

Distribution of handedness and mean HI scores for unimanual reaching in each species.

Ape species	#L	#A	#R	HI	SE	t	p	d
Pongo	12	17	20	0.070	0.056	1.308	0.197	0.378
Gorilla	10	28	28	0.147	0.044	3.297*	0.003	0.779
Chimpanzee	96	129	129	0.044	0.021	2.030*	0.043	0.216
Bonobo	23	33	39	0.053	0.041	1.420	0.159	0.292

*Indicates significant bias. Effect sizes were determined using Cohen’s d.