Spatial modulation of facial expression: enhanced recognition of faces behind the observer

Our ability to recognize facial expressions is crucial for understanding others’ emotions ¹ and facilitating smooth communication ² . Numerous studies have explored how we perceive these cues, considering factors such as health ³ , social signals ⁴ and personality traits ⁵ . However, most of this research involves observers facing a monitor and assessing facial stimuli presented directly in front of them. Real-life scenarios offer more diverse spatial dynamics, such as conversing with someone at a table or glancing back at a passerby. Thus, faces behind the observer might trigger heightened recognition, akin to reacting swiftly to a perceived threat. Herein, we demonstrate that facial expression recognition is influenced by spatial relationships, i.e., faces in front of versus behind the observer. Participants judged the expressions of faces appearing in front of or behind them in virtual space. The findings of three experiments reveal an enhanced level of recognition for faces behind the participant. Interestingly, this effect varies with emotional valence; anger is amplified merely by the presence of a face behind the observer, while happiness requires actively turning to the rear for enhancement to occur. These findings suggest a biological instinct for perceiving threats behind us, potentially influencing subsequent actions. Hence, spatial relationships may modulate facial expression recognition.