[Producing a sequence of movements in response to a sequence of visual stimuli. Inter-individual differences in early phase of sequence learning].

In this work, we studied the inter-individual variants at the early stage of serial learning in the sequence reproduction task where subjects were asked to produce a sequence of movements whose serial order was given by the sequence of visual stimuli. A total of 20 adults participated in the experiment where, besides the sequence reproduction task, each subject also performed the simple visuomotor reaction time task, the choice reaction time task and the serial reaction time task. It was found that individual latencies vs. trial number plots (learning curves) were characterized by one distinctive feature: the latency reduction, if any, took a form of either an abrupt decline down to a stationary level (fast phase) or a gradual approximately linear leveling off over the entire block of 60 trials (slow phase). The diversity of the individual learning curves were limited to the following four types: a flat curve, a curve with the fast phase only, a curve with the slow phase only, and a curve that combined both phases with the leading fast phase followed by the slow phase. All the subjects were subdivided into four groups according to the subject's type of learning curve. We analyzed the correlation pattern between temporal indices (latencies and inter-response intervals) and compared these indices to simple visuomotor reaction time, choice reaction time and the amount of learning in the serial reaction time task. The significant between-group differences found in this analysis suggest that there are some essential functional differences related to the group break up. It was suggested that inter-individual variants in the character of the early stage of sequence learning are determined mainly by the functional and structural complexity of the internal representation of the sequence and by the way the working memory operates in order to recognize the driving sequence of visual stimuli and to translate the internal representation of a sequence into motor commands.