Spider fear linked to stronger facing-the-viewer bias

Detecting whether others are approaching or moving away is fundamental for adaptive behavior. This is particularly true under uncertainty where perceptual interpretations are shaped by expectations and affective states such as fear. The present study examined whether anxiety-relevant stimuli systematically bias directional perception when biological motion is ambiguous. We used point-light walkers—minimal displays of moving dots marking the major joints of an agent—to investigate biological motion perception. When orthographically projected onto the frontal plane, these displays are perceptually bistable and can be interpreted as either approaching or receding. Observers typically resolve this ambiguity by perceiving the agent as approaching, a phenomenon known as the facing-the-viewer bias. Despite its potential significance for threat detection, evidence regarding the influence of anxiety-related traits on the bias has been inconsistent. We therefore measured the facing-the-viewer bias across point-light walkers of different species (human, cat, spider) and walking orientations to study its modulation by spider fear. For this, participants with varying levels of spider fear (N = 100) completed a perceptual judgment task indicating the perceived walking orientation of point-light walkers. Results revealed a robust facing-the-viewer bias across species and orientations. Critically, higher spider fear was associated with a stronger bias particularly for frontally oriented spiders. These findings suggest that the facing-the-viewer bias reflects a core sociobiological mechanism for prioritizing potentially approaching agents, which becomes selectively amplified in the presence of fear-relevant stimuli—underscoring how affective expectations can shape perceptual interpretation during ambiguous encounters with feared animals.