Hand preference during behavioral tests and spontaneous activity in two species of common marmoset (Callithrix jacchus and Callithrix penicillata).

Hand preference in two adult C. jacchus (one male and one female) and five C. penicillata (three adult females and two 70-day-old male and female infants) was examined in this study. Animals were housed in large wire mesh cages and daily tested twice during 40 consecutive days in 15-minute experimental sessions. Tests were carried out with dog food pellets and were as follows: 1) food taking from a glass cylinder (12 cm long x 5 cm diameter), 2) food taking from an opaque plastic flask (11 cm long x 9.5 cm diameter) behind wire mesh, 3) food taking under the cage floor and 4) spontaneous activity (food manipulation, self-grooming and scratching behavior, and grasping wire mesh). It was observed that 1) subjects exhibit a high manual ability in all testing conditions, 2) hand biases occurred, but the subjects either reversed hand preference or the preference was ambiguous as the performances are examined in a longitudinal perspective, 3) hand biases were clearly more visible in test 1, which may be due to the complexity of this task itself, 4) hand biases were not similar in all testing conditions--i.e., subjects were left--in one test and right-handed in another-, and 5) the main results were very similar in both C. jacchus and C. penicillata and seem to be not dependent on either sex or age.