Understanding sleep's impact on attitude change : insights from evaluative conditioning and counter-stereotype learning

Abstract

Through the sleep/wake manipulation commonly used in memory research, we incorporate two lines of research that have been largely studied in parallel. Traditional attitude research focuses on the mechanism underlying new attitude formation and the modification of pre-existing attitudes, whereas sleep research has made substantial efforts to reveal sleep’s unique role in supporting memory consolidation. We choose two well-studied topics under attitude research, evaluative conditioning and implicit stereotypes, to investigate whether sleep facilitates adaptive learning of new evaluations and induces durable changes in old stereotypes. Adaptive behavior requires that organisms pick up regularities and form attitudes toward objects and people. Such regularities include not only which stimuli tend to co-occur (e.g., whether stimulus A co-occurs with unpleasant stimulus B), but also how co-occurring stimuli are related (e.g., whether A starts or stops B). In Chapter 2, with a relatively large sample for sleep and memory research (N=200), we report a pre-registered study that examined whether sleep supports adaptive evaluative learning by promoting the consolidation of joint memories for stimulus co-occurrences and stimulus relations. Participants learned about hypothetical pharmaceutical products that either cause or prevent positive or negative health conditions. The learning task was followed by measures of evaluative choices and explicit memory (Time 1). After a 12-hour retention interval of either nocturnal sleep or daytime wake, participants completed the same measures a second time (Time 2). Results showed that sleep (1) strengthened the impact of causal product-condition relations on choice responses based on multinomial modeling analyses and (2) enhanced joint memories for stimulus co-occurrence and stimulus relations based on memory preservation analyses. Together, the findings suggest that sleep promotes adaptive evaluative learning via offline memory consolidation. Learned attitudes are, however, not always adaptive. Some attitudes such as stereotypes toward a certain group of people are not only maladaptive but cause tremendous harm to our society. We conducted a pilot and a pre-registered study (Chapter 3) to test whether sleep facilitates counter-bias training (CBT) to reduce implicit gender stereotypes in the long run. CBT combats stereotyping by repeatedly affirming the counter-stereotypic pairs (i.e., Female + Arts). Participants’ implicit stereotypes were measured by the Gender-STEM Implicit Association Test (GS-IAT) at three time points (pre-training, post-training, and 12-hour delay). Results revealed that participants who slept after the CBT did not differ from the wake group in bias reduction (indicated by reduced D scores of GS-IAT) after 12 hours. However, when we conducted a detailed examination of over-time changes in association and control-oriented processes, only those who slept after the CBT had a broader effect of bias reduction, with the activation of both Female + Arts and Male + STEM associations being reduced after 12 hours, whereas participants who were awake only had a reduction in Male + STEM associations. Overall, the results showed that CBT induced a persistent reduction in implicit gender stereotype, and sleep promoted a generalized training effect.