Cognitive control modulates the expression of implicit sequence learning: Congruency sequence and oddball-dependent sequence effects.

Abstract

Implicit sequence learning represents an established paradigm to investigate incidental skill acquisition in a laboratory environment. During a covert task, participants respond to the location of a target appearing over a series of locations according to a complex sequence, which gets violated in a reduced set of control trials. Even though participants are not fully aware of the sequence, they respond faster and more accurately to trials following it, thus expressing sequence knowledge. Recent evidence has challenged the view that such knowledge is applied rigidly and affects performance independently from control influences. Jiménez et al. (2009) highlighted that its expression gets reduced immediately after trials not conforming with the learned sequence—an effect that resembles the congruency sequence effect (CSE) commonly observed in interference tasks. However, such effects can also be alternatively explained in associative terms. In this experimental series we took advantage of the well-known attentional properties of oddball sounds and introduced them as an orthogonal variable with respect to the learning process. We found that oddball sounds also hindered the automatic expression of sequence learning, highlighting an oddball-dependent sequence effect similar to the CSE, but most clearly triggered by cognitive control. Moreover, as illustrated through a simulation with a simple recurrent network (SRN), we showed that the CSE reported in this article under noisier conditions is harder to expect from associative processes.