Unlocking adults’ implicit statistical learning by cognitive depletion

Abstract

Human learning is supported by multiple neural mechanisms that maturate at different rates and interact in mostly cooperative but also sometimes competitive ways. We tested the hypothesis that mature cognitive mechanisms constrain implicit statistical learning mechanisms that contribute to early language acquisition. Specifically, we tested the prediction that depleting cognitive control mechanisms in adults enhances their implicit, auditory word-segmentation abilities. Young adults were exposed to continuous streams of syllables that repeated into hidden novel words while watching a silent film. Afterward, learning was measured in a forced-choice test that contrasted hidden words with nonwords. The participants also had to indicate whether they explicitly recalled the word or not in order to dissociate explicit versus implicit knowledge. We additionally measured electroencephalography during exposure to measure neural entrainment to the repeating words. Engagement of the cognitive mechanisms was manipulated by using two methods. In experiment 1 (n = 36), inhibitory theta-burst stimulation (TBS) was applied to the left dorsolateral prefrontal cortex or to a control region. In experiment 2 (n = 60), participants performed a dual working-memory task that induced high or low levels of cognitive fatigue. In both experiments, cognitive depletion enhanced word recognition, especially when participants reported low confidence in remembering the words (i.e., when their knowledge was implicit). TBS additionally modulated neural entrainment to the words and syllables. These findings suggest that cognitive depletion improves the acquisition of linguistic knowledge in adults by unlocking implicit statistical learning mechanisms and support the hypothesis that adult language learning is antagonized by higher cognitive mechanisms.

Differential activation of a frontoparietal network explains population-level differences in statistical learning from speech

“…There are also reasons to distinguish these frontoparietal networks from the dorsal network for goal-directed attention [ 47 ], despite a similar involvement of dorsal prefrontal regions. In contrast to research showing SL benefits from interfering with this network (e.g., [ 48 , 49 ]), we show that AS hinders learning. Moreover, frontoparietal involvement, which correlates with auditory–motor synchronization, confers a learning benefit during PL.…”

Population-level differences in the neural substrates supporting Statistical Learning

“…There are also reasons to distinguish these fronto-parietal networks from the dorsal network for goal-directed attention (48), despite a similar involvement of dorsal prefrontal regions. In contrast to research showing SL benefits from interfering with this network (e.g., (49,50)), we show that articulatory suppression hinders learning. Moreover, fronto-parietal involvement, which correlates with auditory-motor synchronization, confers a learning benefit during passive listening.…”

Less is more: Depleting cognitive resources enhances language learning abilities in adults.

“…It also confirms an earlier finding from the language learning literature showing that adults learning an unfamiliar sign language tend to generalize more successfully under distraction (Cochran et al, 1999). The findings are moreover highly in line with very recent work from our lab that shows enhanced speech segmentation abilities (i.e., implicit statistical learning) in adults where the higher cognitive system is depleted, either by using Transcranial Magnetic Stimulation (TMS) to the left dorsolateral prefrontal cortex (DLPFC) or by using the presently used TloadDback task (Smalle et al, 2021). Together, our findings corroborate the idea that a continuously available learning mechanism (i.e., implicit statistical learning) can give rise to discontinuous language outcomes due to changes in the cognitive system (Thiessen et al, 2016).…”

“…Language learning is complex and involves unconsciously picking up statistical regularities from continuous streams of speech sounds, such as word boundaries or rules on phoneme order. Our research findings over the past 5 years, which combine various language learning paradigms, converge toward the idea that higher cognitive abilities interfere with implicit learning processes in adults (Smalle, Panouilleres, et al, 2017; Smalle, Muylle, et al, 2017; Smalle et al, 2016; Smalle et al, 2018; Smalle et al, 2021). New evidence suggests that the ability to synchronize speech movements with auditory speech rhythms is associated with the ability to learn language (Assaneo et al, 2019).…”