Influence of metrical structure on learning of positional regularities in movement sequences

Sequential stimuli are usually perceived to have hierarchical temporal structures. However, some of these structures are only investigated in one type of sequence, regardless of the existing evidence, showing the domain-generality of the representation of these structures. Here, we assess whether the hierarchical representation of regularly segmented action sequences resembles the perceived metrical patterns that organize the representation of events hierarchically in temporally regular sequences. In all our experiments, we presented the participants with sequences of human movements and tested the perception of metrical pattern by segmenting the movement streams into temporally equal groups containing four movements. In Experiment 1, we found that a movement sequence with temporally equal groupings improves the learning of positional regularities inherent within each group of movements. To further clarify the degree to which this learning mechanism is affected by the perceived metrical patterns, we conducted Experiments 2a and 2b, in which the relative saliencies of the first and last positions in the movement groups, respectively, were studied. The results showed that, although in the learning of positional regularities, the rule-conforming first positions are as effective as when both first and last positions are legal, the last positions are not as influential. Based on these findings we conclude that, in grouped sequences, learning of positional regularities may be modulated by the metrical saliency patterns that are imposed by the temporal regularity of the sequential grouping pattern.