Context Matters: Human Faces Hinder Face Pareidolia

The human visual system readily processes illusory faces (IFs) as faces, a phenomenon known as face pareidolia. Building on evidence that IF processing elicits face-like neural activity and is sensitive to contextual cues, we investigated, via two experiments, whether and how the presence of human faces as a visual context to IFs influences IF categorization. In Experiment 1, we exploited the frequency-tagging approach in EEG to display IFs within rapid sequences of various object categories, interleaved with either human faces (face context, FC) or houses (nonface context, NC). The IF-selective neural response was significantly weaker and less face-like in FC compared to NC, with different topographical and temporal patterns. In Experiment 2, another group of participants performed an explicit IF detection task and exhibited slower RTs and lower detection accuracy in FC than in NC, consistent with the neural findings from Experiment 1. These results suggest that, rather than facilitating IF categorization, the presence of human faces interferes with IF categorization, likely because they compete for the same face-selective resources. Overall, this research highlights the critical role of context in shaping visual categorization by demonstrating earnestly how the visual environment dynamically influences the neural and perceptual processing of ambiguous stimuli.