Table 4.
Task-specific handedness in captive chimpanzees
| Measure | #R | #A | #L | HI | s.e. | t-value |
|---|---|---|---|---|---|---|
| Throwing (n = 89) | 50 | 16 | 23 | .30 | .091 | 3.81** |
| Gesture (n = 347) | 169 | 133 | 45 | .26 | .025 | 10.17** |
| TUBE (n= 542) | 272 | 118 | 152 | .14 | .024 | 5.69** |
| Ball (n = 54) | 31 | 14 | 9 | .28 | .083 | 3.59 ** |
| Reaching (n = 345) | 105 | 161 | 79 | .03 | .022 | 1.49 |
| Tool Use (n =192) | 63 | 52 | 74 | −.06 | .040 | −1.42 |
| Coconut (n = 157) | 61 | 32 | 64 | −.01 | .054 | −0.23 |
| Bimanual Feeding (n = 185) | 73 | 65 | 47 | .08 | .032 | 2.34 * |
| (T) Grooming (n = 200) | 48 | 49 | 103 | .03 | .032 | 0.95 |
| (B) Grooming (n= 125) | 28 | 84 | 13 | .13 | .042 | 2.95 ** |
| (U) Grooming (n = 178) | 52 | 78 | 48 | -.01 | .036 | −0.17 |
*
p < .05
**
p < .01.
(T) reflects total frequency in right and left hand use for grooming, (B) bimanual grooming, (U) unimanual grooming. #R = number or right-handed, #A = number of ambiguously-handed, #L = number of left-handed. Hand preference classification were based on z-scores calculated on the basis of frequencies in left and right hand use for each task. Subjects with z-scores ≥ 1.96 were classified as right-handed, those with z-scores ≤ −1.96 were classified as left-handed. All others were classified as ambiguously-handed.