The effects of sequence structure and reward schedule on serial reaction time learning in the monkey

This research tests the hypothesis that sequence learning performance in no n-human primates will be modulated both by the structure of the sequences t o be learned and by the schedule of reward applied during learning. Sequenc e learning in humans has been extensively explored with serial reaction tim e (SRT) protocols where learning is revealed by reduced reaction times for stimuli presented in repeating sequences vs. stimuli presented in random se ries. The SRT protocol has been used to demonstrate that different types of sequential structure may be learned under different awareness conditions. Here, we consider surface and abstract structure of sensorimotor sequences such that sequences ABCBAC and DEFEDF (where A to F correspond to spatial l ocations on a touch sensitive screen) have different serial order or surfac e structure, but share the same abstract structure 123213, and are thus con sidered isomorphic, in four experiments, we manipulated the type of sequent ial structure to be learned, and the schedule of reward in spatial sequence learning tasks. Both of the two monkeys tested demonstrated significant SR T learning for serial order or surface structure, while they failed to lear n and transfer abstract structure. Their learning performance was also modu lated by the schedule of reward. These results are in support of our hypoth esis and are discussed in the context of existing models of sensorimotor se quence learning. (C) 2000 Elsevier Science B.V. All rights reserved.