Visual statistical learning is not reliably modulated by selective attention to isolated events

Recent studies of visual statistical learning (VSL) have indicated that the visual system can automatically extract the temporal and spatial relationships between objects. We report several attempts to replicate and extend earlier work (Journal of Experimental Psychology: General, 134, 552-564, 2005) in which observers performed a cover task on one of two interleaved stimulus sets, resulting in the learning of temporal relationships that occurred in the attended stream, but not those present in the unattended stream. Across four experiments, we exposed observers to similar or identical familiarization protocols, directing attention to one of two interleaved stimulus sets; afterward, we assessed the VSL efficacy for both sets using either implicit response time measures or explicit familiarity judgments. In line with prior work, we observed learning for the attended stimulus set. However, unlike in previous reports, we also observed learning for the unattended stimulus set. When instructed to selectively attend to only one of the stimulus sets and ignore the other set, observers could extract temporal regularities for both sets. Our efforts to experimentally decrease this effect by changing the cover task (Exp. 1) or the complexity of the statistical regularities (Exp. 3) were unsuccessful. A fourth experiment using a different assessment of learning likewise failed to show an attentional effect. Simulations drawing random samples from our first three experiments (n = 64) confirmed that the distribution of attentional effects in our sample closely approximated the null. We offer several potential explanations for our failure to replicate earlier findings and discuss how our results suggest limiting conditions on the relevance of attention to VSL.