Schlaghecken, F., Stuermer, B., & Eimer, M. (2000). Chunking processes in the learning of event sequences. Memory & Cognition, 28, 821-831.
It was investigated whether effects of implicit learning (IL) are due to well learned and explicitly represented fragments of the stimulus material ('chunks'). To this purpose, event-related brain potentials (ERPs) were recorded during an oddball-version of a serial RT task: At unpredictable positions within a 16-item letter sequence, single deviant items replaced an item of the repeatedly presented standard sequence. After acquisition, the 'process dissociation procedure' (Jacoby, 1991) was adopted to identify explicitly learned sequence parts for each participant. Acquisition of sequence knowledge was reflected in faster RTs for standard as compared to deviant items, and in enhanced N2b and P3b components for deviant items. While the ERP effects were obtained for explicitly represented sequence parts only, RT effects were independent of subsequent reproduction performance. These results indicated that (i) ERPs are a valid measure of explicit knowledge; (ii) implicit and explicit knowledge co-exist in serial RT-tasks; and (iii) chunking processes play a major role in the acquisition of explicit knowledge about event sequences.