Modulating social learning-induced evaluation updating during human sleep

Abstract

People often change their evaluations upon learning about their peers' evaluations, i.e., social learning. Given sleep's vital role in consolidating daytime experiences, sleep may facilitate social learning, thereby further changing people's evaluations. Combining a social learning task and the sleep-based targeted memory reactivation technique, we asked whether social learning-induced evaluation updating can be modulated during sleep. After participants had indicated their initial evaluation of snacks, they learned about their peers' evaluations while hearing the snacks' spoken names. During the post-learning non-rapid-eye-movement sleep, we re-played half of the snack names (i.e., cued snack) to reactivate the associated peers' evaluations. Upon waking up, we found that the social learning-induced evaluation updating further enlarged for both cued and uncued snacks. Examining sleep electroencephalogram (EEG) activity revealed that cue-elicited delta-theta EEG power and the overnight N2 sleep spindle density predicted post-sleep evaluation updating for cued but not for uncued snacks. These findings underscore the role of sleep-mediated memory reactivation and the associated neural activity in supporting social learning-induced evaluation updating.

Fig. 1. A flowchart of the experiment procedure.

a The experiment included pre-learning baseline tests, a social learning task in which participants learned their peers’ evaluations, post-learning immediate tests, TMR during NREM sleep, post-TMR tests, and 3-day delayed tests. We determined the immediate ΔEvaluation as the difference between pre-and post-learning, overnight ΔEvaluation as the difference between post-learning and post-TMR, and delayed ΔEvaluation as the difference between post-learning and delayed phases. b An exemplar trial in the Evaluation tasks: Participants evaluated each of the 48 snacks using a mouse clicking on a 1-11 scale, ranging from not preferred at all (1) to most preferred (11). c During the Social Learning task, participants learned the evaluation from their peers (a circle indicating their peers’ evaluation) while hearing the spoken names of the snacks upon the onset of the peers’ evaluations. Half of these auditory cues were then re-played during the following NREM sleep to reactivate the social learning memories (i.e., peers’ evaluation toward the snack). This resulted in six experimental conditions (Higher_Cued vs. Uncued; Lower_Cued vs. Uncued; Consistent_Cued vs. Uncued). The snack picture is from Hare et al..

Fig. 2. Impact of feedback and TMR on evaluation updating across phases.

Effects of feedback (i.e., peers’ ratings either higher or lower than pre-learning baseline ratings) and TMR (cued vs. uncued) on ΔEvaluation from (a) pre-learning to post-learning, (b) post-learning to post-TMR, and (c) post-learning to delayed phases. The error bars indicate the standard error of the mean (S.E.M.). The horizontal gray dashed line represents the mean of ΔEvaluation at the corresponding phase. ***: p < 0.001. *: p < 0.05.

Fig. 3. Impact of subsequent memory, feedback and TMR on evaluation updating across phases.

Effects of subsequent memory, TMR, and feedback on ΔEvaluation from (a) pre-learning to post-learning, (b) post-learning to post-TMR, and (c) post-learning to delayed phases. The horizontal lines indicated the 95% highest density interval (HDI), and the vertical gray lines correspond to 0. The dot indicates the median. If the 95% HDI does not encompass 0, the result is significant.

Fig. 4. Cue-elicited EEG Power and ΔEvaluation.

a Memory cue (higher, lower, and consistent) and (b) control cue-elicited power spectral averaged across nine fronto-central channels (F1/2, Fz, FC1/2, FCz, C1/2, Cz). The topography on the left-top and right-top corners indicated the power at all 61 channels at the early and late clusters, respectively. The contour highlighted significant clusters. The effect of memory cue-elicited delta-theta power (1–8 Hz) on ΔEvaluation of cued snacks from (c) post-learning to post-TMR and (d) post-learning to delayed phases. The black line below the red and blue density plots indicated the 95% highest density interval (HDI) for higher and lower feedback conditions, respectively. The bottom black line indicates the difference between higher vs. lower feedback conditions. The dot indicates the median point. If the 95% HDI does not encompass 0, the result is considered significant.

Fig. 5. Relationship between overnight N2 spindle density and evaluation updating across phases.

The relationship between overnight N2 Spindle Density and (a) overnight and (b) delayed ΔEvaluation. The left figure shows the effect on the cued snacks, while the right figure represents the effect on the uncued snacks. The vertical gray lines correspond to 0. The horizontal red and blue lines indicated the 95% highest density interval (HDI) for higher and lower feedback conditions, respectively. The bottom black line indicates the difference in higher vs. lower feedback conditions. The dot indicates the median. If the 95% HDI does not encompass 0, the result is considered significant.