Humans typically acquire information in social contexts. Therefore, we investigated its role for long-term recognition memory and encoding ERPs for positive, negative, and neutral words. We compared a group for whom a social context was induced via a self-introduction followed by evaluative feedback (“social-feedback” group) with a verbal-learning and a standard levels-of-processing group. Although the social-feedback group was not aware of the recognition session one week later, this group showed superior recognition accuracy, but also an increased response bias, particularly for positive adjectives. Encoding ERPs revealed the highest EPN and LPP amplitudes in the social-feedback group. Only in the slow-wave window were ERPs most positive-going in the verbal-learning group. ERPs from the levels-of-processing group fell in between the other two. Together, these findings reveal a distinct effect of evaluative social context, enhancing long-term recognition memory and encoding ERPs beyond both explicit learning and standard levels of processing manipulations, while also inducing specific biases.
The highest memory accuracy in the social feedback group indicates that the social context facilitated memory encoding, likely via elaborative stimulus processing which is known to enhance memory (Fisher & Craik, 1977; Sui & Humphreys, 2015; Symons & Johnson, 1997). Since explicit learning tasks are typically easier and result in better memory than incidental ones (Rugg et al., 1998; Wang, 2020), these findings highlight the power of social context to increase stimulus encoding.
Groups also differed in their response bias, with less conservative responses in the social-feedback and the verbal learning groups. Moreover, the social-feedback group was specifically biased towards classifying positive words as “old”. Healthy participants are known to have optimistic feedback expectations (Hepper et al., 2011), leading to distorted memory when information is incongruent with their positive self-view (Story, 1998). In fact, better than expected evaluations induce positively biased self-updating (Korn et al., 2012) as well as a specific feedback-related positivity (Schindler et al., 2021). Self-serving tendencies also occurred in feedback acceptance (social-feedback group) and self-descriptiveness decisions (levels-of-processing group), the highest acceptance rates for positive adjectives corresponding with positive self-views of healthy participants (e.g., see Sharot & Garrett, 2016).
Concerning ERPs, words in the social feedback context elicited the largest EPN and LPP amplitudes, followed by levels-of-processing and, finally, instructed learning. Per se, these ERP modulations are broadly in line with findings of increased EPN and LPP amplitudes for various manipulations of self-reference and social feedback (e.g., see Bayer et al., 2017; Fields & Kuperberg, 2012; Herbert et al., 2011; Schindler et al., 2015). Given the EPN’s role in early attentional selection (Schupp et al., 2007), results show a rapid prioritizing role of social-evaluative context beyond mere task-relevance. The highest LPP in the social feedback group accords with this component indexing successful memory encoding (Dolcos & Cabeza, 2002).
Finally, only in the slow-wave window were ERPs more positive-going in the verbal-learning group than in the other two groups. Given the role of positive-going slow waves in strategic verbal memory encoding (Bosch et al., 2001), this finding might explain why the verbal-learning group had similar recognition accuracy (and even more hits) than the levels-of-processing group, despite having smaller amplitudes on the earlier ERPs. Therefore, encoding in the social feedback and levels-of-processing groups seems to have relied more on automatic mechanisms, whereas the verbal-learning group recruited more strategic processes—exploratory correlations accord with this interpretation (see Supplementary Materials Section B).
As expected, significant emotion effects on brain potentials were also observed, although they were smaller than the context-effects. Emotion sensitivity of EPN and LPP components aligns with much previous research (e.g., see Hinojosa et al., 2010; Kissler et al., 2007; Rohr & Abdel Rahman, 2018; Schacht & Sommer, 2009). Largest amplitudes for positive words have also been reported before (e.g., Herbert et al., 2008). Self-referential processing might have contributed to a more substantial increase for positive content, whereas in other situations a bias towards negative material might occur (e.g., see Hinojosa et al., 2010; Schacht & Sommer, 2009).
Overall, we show that social context during encoding enhances long-term recognition memory beyond explicit learning or typical deeper incidental encoding tasks (self-descriptiveness or concreteness decisions). Notably, although both the social feedback and self-descriptiveness task probably recruited self-referential processing, effects in the feedback condition, where any self-reference was socially contextualized, by far exceeded those of task-driven self-referential processing alone. Although the retention interval leaves ample time for consolidation or spontaneous rehearsal, which we cannot directly assess, the immediate repetition run revealed no significant effects, suggesting that effects were either due to initial encoding, where corresponding ERP modulations occurred, or arose considerably later.
Our focus was on the between-groups analysis, which de-emphasizes potentially interesting effects in individual conditions. Still, in Experiment 1, some “sender” differences occurred at encoding (see Supplement C), replicating previous research (e.g., see Schindler et al., 2019). However, these had little effect on long-term recognition, suggesting that participants integrated both blocks from experiment 1 into one episode whose items were considerably more memorable than those from the other two experiments. Interactions in the levels-of-processing group indicate that encoding task modulates emotion effects in long-term recognition memory, only self-descriptiveness and not concreteness decisions resulting in an emotion effect on recognition accuracy, in line with the suggestion of interacting memory effects of self and emotion (see Gutchess & Kensinger, 2018).
In sum, although we used identical stimuli and presentation parameters across three experiments, the psychological encoding contexts elicited pronounced between-group differences in recognition memory and ERPs: The social-feedback context enhanced recognition memory beyond both explicit verbal-learning and self-descriptiveness/concreteness judgments. It also induced the largest EPN and LPP amplitudes, followed by levels-of-processing and verbal learning. The most positive-going slow wave amplitudes in the verbal learning group suggest that this group might have relied particularly on strategic memory processes. Our findings specify some important social factors in human long-term memory. They resonate with the fact that humans typically acquire information in social contexts (e.g., see Light & Perret-Clermont, 1991), social evaluation being a particularly salient factor in human life (e.g., see Moor et al., 2010). Finally, these results have implications for memory formation in educational settings or memory assessment in legal contexts, where the extent to which individuals were exposed to an evaluative social context will affect their memory for elements of the initial episode.