Language learning in a stressful world: individual differences in cardiac responses to stress and recovery predict statistical learning

Abstract

Learning in adulthood is embedded in everyday social life, in which periods of psychosocial stress alternate with recovery. In such a dynamic environment, the autonomic nervous system regulates bodily responses, including cardiac activity. Individuals differ in their capacity for bodily regulation, but it remains unknown whether these differences modulate statistical learning. Here, we investigated learning of probabilistic patterns in speech streams, i.e., statistical language learning, in a six-hour experiment incorporating psychosocial stress and recovery to approximate everyday conditions. Sixty-five adults were exposed to speech streams in conditions with and without acute stress induction, with learning assessed immediately after exposure and following a rest period. Heart rate variability was recorded throughout the experiment to capture individual differences in cardiac responses across stress and recovery periods. From these measures, we constructed composite proxies of cardiac mobilization during acute stress and cardiac vagal recovery during rest. Individuals with congruent cardiac mobilization and cardiac vagal recovery composite scores, either jointly high or jointly low, showed superior statistical learning outcomes across learning conditions. Cardiac mobilization was positively correlated with immediate performance, i.e., encoding of probabilistic patterns. In contrast, cardiac vagal recovery was positively correlated with post-rest performance, i.e., consolidation. Moreover, the association between momentary cardiac mobilization during speech exposure and statistical learning depended on individuals' cardiac mobilization composite scores. These findings demonstrate that individual differences in cardiac regulation are closely linked to the ability to learn statistical dependencies in the environment involving changing physiological demands. Overall, the findings highlight the role of bodily regulation in statistical language learning.