Evidence for Lasting Sequence Segmentation in the Discrete Sequence-Production Task

Abstract

It is well known that movement sequences are initiated and executed more slowly as they become longer. Those effects of sequence length, which have been found to lessen with practice, have been attributed to the development of a single motor chunk that represents the entire sequence. But an increasingly efficient distribution of programming can also explain the effects. To examine the mechanisms underlying skill in executing keying sequences, the authors examined the performance of participants (N = 18) who practiced a discrete sequence-production task involving fixed sequences of 3 and 6 key presses. Detailed examination of the effects of extensive practice, of regularities in key pressing order, and of a preceding choice RT task on the production of those sequences showed that most participants executed the 6-key sequence as 2 or more successive segments and continued to do so in the various conditions. The preceding choice RT task restored the sequence-length effect in latency that had disappeared with practice. The present results suggest that practice induces the development of motor chunks, each representing a short segment, and with longer sequences a control scheme for concatenating the motor chunks. Segmentation of longer sequences appeared to be concealed by individual segmentation differences unless there were regularities that imposed a common segmentation pattern.

Skill in discrete keying sequences is execution rate specific

“…This spontaneously developing slow response was attributed to the concatenation of successive motor chunks because motor chunks would be limited to 3-5 responses (e.g., Abrahamse et al, 2013;Verwey, 2003a;Verwey & Eikelboom, 2003). The present finding of a slow R 5 shows that this slow response is not specific for the sequences used in those earlier studies, as we here used different sequences 4 .…”

Differences in chunking behavior between young and older adults diminish with extended practice

“…Note that the left plot seems to suggest that the 6-element sequence was performed as one large chunk, since no clear slow elements are visible. This is not the case, this RT profile simply results from averaging over multiple participants who have slow elements at different locations (Verwey & Eikelboom, 2003) was significant too, F(8, 272) = 5.2, p = 0.003, η p 2 = 0.13, and the main effect of Age group did not reach significance either. This time, however, Block interacted with Age group, F(8, 272) = 3.5, p = 0.019, η p 2 = 0.09, suggesting that the older participants benefited more from the additional practice than the young participants did (see Fig.…”

“…Second, it takes into account the potential confounding effects of fingers that are slow in general. Third, chunking structures differ per participant (Verwey & Eikelboom, 2003), something that our analysis took into account. Finally, using this method allows us to, indirectly, compare outcomes of our study to previous DSP chunking studies in older adults (Verwey, 2010;Verwey et al, 2011) A downside of our t test based method that we could not overcome is that of the 6 elements, only RT 3, 4 and 5 can be a slow element.…”

Learning and production of movement sequences: Behavioral, neurophysiological, and modeling perspectives

“…The results were in line with the notion that practice a11ows the processes that arc: required for executing individual elements to overlap with execution of the preceding clement. Evidence for one hypothesized type of motor chunk development, an increasing execution rate with serh1l position due to an increasing spread of activation across sequence elements (MacKay, 1982), was not found (also sec Verwey, 1999;Verwey & Eikclboom, 2003).…”