New Use of the Facial Adaptation Method: Understanding what Facial Expressions Evoke Social Signals

Adaptation changes the perception of subsequent stimuli that share the same processing as the adapting stimulus: adaptation to sad or fearful facial expressions leads to the reduction of the perception of sad or fearful, respectively. Facial expressions also have the function to convey social messages. This study examined whether and how adaptation to facial expression affects these social signals using the perception of the need to help this person (NH) and the motivation to help them (MH), which both sad and fearful facial expressions evoke. Participants rated NH and MH of sad and fearful facial expressions after adapting to sad or fearful facial expressions. If we adapt to social signals as well as facial expressions, the perception of the help signal will change after adapting to facial expressions. The results showed that after adaptation to sad expressions in Experiment 1, NH decreased in both sad and fearful facial expressions. After adaptation to fearful expressions in Experiment 2, it decreased only in fearful and not in sad facial expressions. MH did not change before and after adaptation in both experiments. To eliminate the possibility that the adaptation to sad facial expressions altered the sensitivity to any facial expressions, participants judged the perception of sadness and fearfulness of faces after adapting to sad facial expressions in Experiment 3. The results showed that only the perception of sadness of sad facial expressions decreased. Therefore, adaptation to sad facial expressions impaired perception of sadness and reduced the social signals of the need for help in both sad and fearful facial expressions, suggesting that sad facial expressions automatically evoke the message of the need for help, but fearful facial expressions do not. This study demonstrates that facial adaptation is an effective tool for understanding what facial expressions automatically evoke social signals.