Serial correlation in lateralized choices of hand and target

We investigated how lateralized choices of hand and target are influenced by previous behavior. Three monkeys retrieved food pellets following cues indicating the location of available food pellet targets, and the hand that could be used to acquire a target. In pseudo-randomized trials, the monkeys could retrieve food pellet targets only on their right side, only on their left side, or their choice of either right or left side, using only their right hand, only their left hand, or their choice of either hand. We examined separately the patterns of serial correlation in target choices and hand choices. Although individual monkeys showed overall laterality preferences, instead of repeatedly using the preferred hand, we found that the monkeys tended to switch hands in successive trials. This serial correlation in hand choice was stronger and more robust than serial correlation in target choice. Furthermore, the pattern of serial correlation for target choice closely resembled that of serial correlation for hand choice when the animal was allowed to choose both target and hand, but only when the target cue was presented before the hand cue. These results suggest that when cued to choose a hand first, the monkeys tended to make a separate decision as to whether to switch their target choices or not, whereas their decisions to switch hands and targets were linked more tightly if the animal was cued to choose a target first.