Implicit Learning: A Demonstration and a Novel SRT Paradigm

Abstract

Evidence for human learning without awareness of what is learned has been sought in serial reaction time (SRT) tasks in which, unknown to participants, the locations of stimuli follow a particular rule or sequence (Willingham, Nissen & Bullemer, 1989). A number of criticisms have been levelled at such tasks, including a lack of adequate control for sequential effects and a discrepancy in sensitivity between measures of implicit and explicit knowledge about the task (Jones & McLaren, 2009; Shanks & St. John, 1994). In this study we provide a novel, two-choice SRT paradigm whereby the locations of the response stimuli are sometimes predicted by a separate set of stimuli on screen. A color-filled square appears before each stimulus requiring a response, with participants informed this is simply a fixation point to prepare for the next trial. Two out of eight colors are predictive on 80% of trials, and performance on these consistent trials was faster than on the other six colors that were equally likely to result in either of the two possible responses. All these trial types were faster and more accurate than the remaining inconsistent 20% of trials for the predictive colors, which also produce more errors than control colors. A prediction task and interview followed the task, on which participants performed at near (slightly below) chance levels. We suggest that this task is a useful tool for studying associative learning in humans, as it provides reliable effects that appear to demonstrate implicit learning with relatively brief training.