Acquisition of the temporal and ordinal structure of movement sequences in incidental learning

We investigated the acquisition and integration of temporal and ordinal sequence information in an incidental learning model of motor skill acquisition (the serial reaction time task). Human participants were exposed to a stimulus-response sequence that had temporal structure, ordinal structure, or both. By changing the temporal or ordinal structure, or both, we were able to ask two questions: first, does a regular temporal structure facilitate learning of an ordinal sequence and second, is a temporal sequence, presented in the context of a random ordinal sequence of finger movements, "picked up" through incidental learning? We found that a predictable temporal structure greatly facilitated the learning of an ordinal sequence but was not learned when presented in isolation. The results suggest that when motor skills are acquired under incidental learning conditions, timing is represented at a level specific to the ordinal sequence of movements rather than as an independent temporal template.