Academic journal article Memory & Cognition

Oculomotor Evidence of Sequence Learning on the Serial Reaction Time Task

Academic journal article Memory & Cognition

Oculomotor Evidence of Sequence Learning on the Serial Reaction Time Task

Article excerpt

Manual and oculomotor measures of sequence learning were examined on the serial reaction time (SRT) task. Participants were assigned into four groups differing on response modality (manual, oculomotor) and trial type (sequence, pseudorandom). The pattern of manual RTs replicated previous studies. Frequency of anticipatory eye movements followed similar patterns as RTs. Participants made many anticipations, even in pseudorandom blocks, and frequency of anticipations did not depend on presence of concurrent manual responses. Excluding participants with explicit awareness did not change results. Anticipations were negatively related to RTs in both incidental and intentional learning. Anticipations were positively related to sequence recall in intentional, but not incidental, learning. Results suggest that (1) anticipatory eye movements reflected sequence learning and (2) participants made overt and covert shifts of visuospatial attention to likely stimulus locations prior to stimulus onset, whether or not they made manual responses and whether or not there was a sequence.

Whether or not we are aware of it, many activities in our daily lives require the ability to extract regularities from environmental input and to act on the basis of these internal representations. One aspect of this remarkable ability is learning to extract regularities in sequential stimuli and to execute corresponding sequences of actions.

Sequence learning is often measured on the serial reaction time (SRT) task (Nissen & Bullemer, 1987). The advantage of this task is that it assesses sequence learning through performance measures during the task, rather than through recall or recognition measures administered later. On this task, series of stimuli are displayed briefly in one of several (typically three or four) locations arranged horizontally on a computer screen. Participants respond by pressing buttons corresponding to the locations. Although participants are not informed of this, the stimuli sometimes follow a repeating sequence (typically, 10 or 12 items in length) presented multiple times across blocks. As the sequences recur, manual RTs decrease. When random trials are later presented, RTs increase. The interpretation of these RT changes is that sequence learning has occurred. Because direct measures typically show that awareness of the sequence is poor, the SRT task has been interpreted as demonstrating a predominantly implicit form of learning.

The SRT task has been very useful in investigating sequence learning in healthy adults and clinical populations. Our goal in using this task was to extend this research to typically developing and psychiatrically impaired children. However, one problem in testing clinical and developmental populations on any task in which manual RT is the main dependent variable is the issue of response speed. When there are differences between age groups or between clinical and healthy groups in speed of musculoskeletal responses, it is difficult to tease apart developmental or clinical differences in sequence learning from differences in motor output (cf. Helmuth, Mayr, & Daum, 2000).

One way to circumvent this problem is to assess performance using eye movements, which are less affected by developmental and clinical factors. Thus, if eye movements can be shown to reflect sequence learning on the SRT task, then an oculomotor version of the task could be helpful in developmental and clinical studies. Therefore, the primary goal of this study was to develop an oculomotor version of the SRT task by comparing eye movements and manual responses of healthy adult participants who only looked at the stimuli with those of participants who both looked and made manual responses.

However, a review of the studies on the SRT task reveals that the issue of what participants are actually looking at, and what they may be learning, if anything, when they observe a sequence of stimuli is still far from clear. …

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