A new paper on the relationship between facial expressions and social signals led by Program-Specific Researcher Kazusa Minemoto in collaboration with Associate Professor Yoshiyuki Ueda and Professor Sakiko Yoshikawa (Kyoto University of the Arts) has been published in Psychological Research.

In their study, the researchers investigated whether and how facial expressions like sadness and fear automatically trigger perceptions of social signals such as the need for help. It is known that our perception can become less sensitive to facial stimuli if they are presented after first showing some other ones—a phenomenon called adaptation. Previous studies have shown that various types of facial information (e.g., expressions, identity) can be influenced by this phenomenon. By manipulating the relationship between the preceding and subsequent stimuli, researchers have examined whether the processing of each type of information is independent (unaffected by adaptation) or not (affected by adaptation). However, our understanding of the relationship between facial expressions and social signals is still lacking.

This study started from the idea that both sad and fearful expressions can be evaluated as indicating “a need for help.” Prior research has shown that the processing of these two categories of expression is independent—that is, adaptation to one does not affect perception of the other. In the current experiment, participants viewed the expressions before and after adaptation and were asked to rate them on how much the expression suggested a “need for help” (perception of the need for help) and how much they “wanted to help” (motivation to provide help).

The results showed that after adapting to sad expressions, both sad and fearful expressions were rated as indicating a lower need for help. This suggests that seeing a sad expression automatically triggers the perception of the need for help, which is then diminished by adaptation. In contrast, after adapting to fearful expressions, only the perceived need for help in fearful expressions decreased, with sad expressions unaffected. One possible explanation for this could be that the perception of fear itself is getting dulled by adaptation. Notably, ratings of helping motivation were unaffected, suggesting that motivation to help in response to sad or fearful expressions involves a more complex decision-making process.

Taken together, the study not only demonstrates that adaptation occurs in response to the social signal of “need for help,” but also shows a new utility of adaptation research: using the adaptation effect to examine which social signals are automatically perceived when specific facial expressions are seen.

The full article is open access and freely available here.

Reference:

Minemoto, K., Ueda, Y., & Yoshikawa, S. (2025). Facial expression adaptation impairs perceived social signal across expressions. Psychological Research, 89(2):73. doi: 10.1007/s00426-025-02094-4.