Learning versus behavioral expression of the learned: The effects of a secondary tone-counting task on implicit learning in the serial reaction task

The replicated finding that implicit learning in the serial reaction task (SRT) is impaired when both the learning and the assessment of learning occur in the presence of a secondary tone-counting task has been interpreted as implying that the mechanism(s) underlying implicit sequence learning require(s) attention in order to operate. However, in almost all studies, learning and the assessment of learning have been confounded. It is therefore unclear whether tone counting affects learning per se, the behavioral expression of the learned, or both. The goal of the present research was to disentangle the effects of tone counting on learning and the expression of the learned. In Exps. la and Ib, participants performed the Nissen and Bullemer SRT under different single-task (ST) and dual-task (DT) practice schedules. In Exps. 2a and 2b, participants received different amounts of ST and DT practice. In all experiments, degree of implicit learning was then assessed under both ST and DT conditions. Results are consistent with the argument that primarily the expression of what has been learned and, to some extent, implicit learning itself, are affected by tone counting. These findings are easily understood in terms of specific interference mechanisms but are problematic for models that contain the assumption of an attentional learning mechanism.