Abstract # 91:

Scheduled for Thursday, June 18, 2015 06:00 PM-08:00 PM: (Cascade AJBCD) Poster Presentation


INDIVIDUAL DIFFERENCES IN HAND PREFERENCE DURING A NOVEL TASK IN COMMON MARMOSETS (CALLITHRIX JACCHUS)

S. J. Neal and N. G. Caine
California State University San Marcos, 333 S Twin Oaks Valley Rd, san marcos, ca 92096, USA
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     In most studies of hand preferences, subjects are tested or observed over many trials and the strength of preference is reported in terms of the relative number of times each hand was used (Handedness Index = R-L/R+L). This approach masks potentially interesting data insofar as we do not pursue an explanation for circumstances in which the non-preferred hand is used. We hypothesized that initial exposures to a novel task might evoke a variety of cognitive and emotional states that engage competing hemispheric specializations, leading to ambilateral hand use. We recorded all-occurrences of hand use in seven common marmosets during ten exposures to a task that required subjects to use one hand to reach inside a tube to obtain food. Three subjects were ambilateral in the initial exposures to the task (HI scores between -0.33 and 0.04), but became strongly lateralized by the fifth exposure (HI scores > 0.54). Three other subjects preferred one hand from the start (HI scores > 0.88). The seventh marmoset exhibited ambilaterality throughout all ten exposures. Except for the seventh marmoset, HI scores previously calculated from 300 instances of spontaneous hand use in everyday situations did not predict how lateralized a marmoset would be in the early exposures to the novel task. Careful examination of variability within individuals’ patterns of hand use may give us additional insight into hemispheric specialization.