The Covid-19 pandemic lockdown had led to unusually mas- sive social isolation that lasted for months around the world. In order to compensate for the poverty of social life, individ- uals are likely to shift their attention from their regular social world to their inner imaginative world during this lockdown pe- riod. Thus, the purpose of this study is to investigate whether intersubject similarity in individuals’ imaginative abilities (i.e., fantasy tendency) is associated with their similarity in affective ratings of the videos they watched, and whether this associa- tion is enhanced during the pandemic lockdown period. We recruited one lockdown group and two post-lockdown groups to test the above hypothesis. During the experiment, partici- pants were asked to watch a series of videos covering a wide range of topics, and then they were asked to complete several affective appraisal ratings (e.g., liking or feeling of resonance) of each video. We then used intersubject representational similar- ity analysis (ISRSA) to map the intersubject similarity in their fantasy tendency onto their similarity in the affective appraisal ratings. Our results showed that those who were more simi- lar in their fantasy scores also showed more similarity in their affective appraisals of videos. Most importantly, this fantasy- appraisal association was particularly strong in the lockdown group, but rather weak in the post-lockdown groups. Our find- ings suggest that individual differences in their imaginative abil- ities would become a crucial factor influencing how individuals appraise their inner world during social isolation. The current study may provide an example for policymakers on how to as- sess the impact of social isolation as we may face another wave of pandemics in the future.

The pandemic lockdown resulted in billions of individuals be- coming socially isolated while being bombarded with unset- tling news through online media outlets. Emotional contagion, which can propagate through means beyond in-person contact, is likely to have played a significant role in amplifying the spread of negative emotions worldwide. Despite the fact that facial be- haviors can become more synchronous under the influence of emotional contagion, it remains unclear whether individuals ex- hibit synchronous negative facial expressions in stressful situa- tions where social contact is limited. To address this gap, this study took a naturalistic viewing approach to record real-time facial behaviors while participants watched a series of pandemic and death-related movie clips in a lockdown group (N=26) and a post-lockdown group (N=32). The facial action unit (AU) fea- tures were extracted from facial videos, and intersubject corre- lation (ISC) was utilized to compute the degree of synchrony across individuals within their respective groups. Lastly, we built a machine-learning model that utilized within-group AU- ISC values as features and accurately classified participants into their respective groups. Our results revealed that the weights of our predictive model closely aligned with expressions of sad- ness and fear, supporting our initial hypothesis that individuals tend to exhibit more synchronized facial behaviors, particularly those associated with negative emotions, during the lockdown period than during post-lockdown periods. Our study offers novel insights that could inform future research into the under- lying mechanisms and implications of synchronized facial be- haviors as a potential collective response to external stressors.