Implicit and explicit contributions to statistical learning

Abstract

Statistical learning allows learners to detect regularities in the environment and appears to emerge automatically as a consequence of experience. Statistical learning paradigms bear many similarities to those of artificial grammar learning and other types of implicit learning. However, whether learning effects in statistical learning tasks are driven by implicit knowledge has not been thoroughly examined. The present study addressed this gap by examining the role of implicit and explicit knowledge within the context of a typical auditory statistical learning paradigm. Learners were exposed to a continuous stream of repeating nonsense words. Learning was tested (a) directly via a forced-choice recognition test combined with a remember/know procedure and (b) indirectly through a novel reaction time (RT) test. Behavior and brain potentials revealed statistical learning effects with both tests. On the recognition test, accurate responses were associated with subjective feelings of stronger recollection, and learned nonsense words relative to nonword foils elicited an enhanced late positive potential indicative of explicit knowledge. On the RT test, both RTs and P300 amplitudes differed as a function of syllable position, reflecting facilitation attributable to statistical learning. Explicit stimulus recognition did not correlate with RT or P300 effects on the RT test. These results provide evidence that explicit knowledge is accrued during statistical learning, while bringing out the possibility that dissociable implicit representations are acquired in parallel. The commonly used recognition measure primarily reflects explicit knowledge, and thus may underestimate the total amount of knowledge produced by statistical learning. Indirect measures may be more sensitive indices of learning, capturing knowledge above and beyond what is reflected by recognition accuracy.

Functional differences between statistical learning with and without explicit training

“…We therefore hypothesized that participants should respond more quickly and elicit a reduced P300 to predictable syllable targets (i.e., those that occur in later syllable positions), reflecting a facilitation in processing due to statistical learning. This result would be consistent with our previous results from this task (Batterink et al 2015). We further hypothesized that if explicit training enhances the function of statistical learning, learners in the explicit condition should show faster RTs and reduced P300s to target syllables compared with learners who have not benefited from explicit training.…”

“…Statistical learning has been demonstrated both when stimuli are presented passively without any explicit task (e.g., Saffran et al 1999;Aslin 2001, 2002;Toro et al 2005), and when participants are engaged in a cover task unrelated to the underlying pattern (Saffran et al 1997, Turk-Browne et al 2005). In addition, statistical learning seems to be unaffected by the precise instructions given to participants (Arcuili et al 2014;Batterink et al 2015). Thus, statistical learning appears to emerge as an obligatory consequence of exposure to input, without requiring explicit guidance to learn.…”

“…First, there is evidence that although statistical learning occurs incidentally or implicitly, it produces knowledge that is at least partially explicit in nature, at least in adult learners (Franco et al 2011;Bertels et al 2012Bertels et al , 2013Batterink et al 2015). Whereas implicit knowledge, such as abstract grammar knowledge (Reber 1967) or perceptual-motor skills (Cohen and Squire 1980) must be acquired over time through direct experience, one feature of explicit knowledge is that it can be provided to learners through explicit instruction (i.e., by verbally transmitting information from one person to another).…”

“…The function of statistical learning was then assessed using an online, speeded, performance-based measure. Known as the target-detection task, this task was originally used in visual statistical learning studies (Turk-Browne et al 2005;Kim et al 2009) and more recently has been adapted to assess statistical learning in the auditory domain (Batterink et al 2015;Franco et al 2015). The task requires participants to respond to target syllables occurring in a continuous syllable stream and provides an indirect measure of statistical learning (Fig.…”

“…1). The target-detection task assesses the extent to which learners use their acquired statistical knowledge to optimize online processing, with faster reaction times (RTs) indexing more efficient processing of predictable targets (e.g., Turk-Browne et al 2005;Kim et al 2009;Batterink et al 2015;Franco et al 2015).…”