The uncanny valley effect and immune activation in virtual reality

The uncanny valley effect describes a phenomenon where humanoid, almost lifelike virtual agents evoke feelings of discomfort in the observers. The Pathogen Avoidance Hypothesis proposes that these feelings are based on a cognitive mechanism that originally evolved to motivate pathogen avoidance. Slight imperfections in virtual agents are thereby misconceived as cues of communicable diseases that elicit disgust and avoidance behavior. Whether uncanny entities also increase mucosal immune responses, particularly when immediate avoidance is impossible, currently remains elusive. The present study examined the link between the uncanny valley and mucosal immune responses by comparing changes in the salivary antibody secretory immunoglobulin A (sIgA). For this, we developed three sets of virtual agents (cartoon, uncanny, and realistic agents) that differed in their human-likeness and uncanniness. Agents were encountered in a social virtual reality (VR) task that required close approach, making avoidance impossible. We found that only the set of uncanny agents who showed slight deviations from normal human appearance, yet were still considered as more human-like than the cartoon agents, evoked a significant increase in sIgA release during social interactions in VR. This conforms to error-management theories suggesting that perceptual systems are biased towards false positive responses to potential contagion cues, reducing the risk of missing actual health threats. Our findings further indicate that presence in virtual reality was likely essential for effective immune activation by uncanny agents, as increased sIgA levels correlated with deeper involvement in the virtual environment. Moreover, the immune response may have been automatically triggered by perceived threats from these agents, as conscious evaluations of interoceptive awareness, state anxiety, and eeriness during VR did not correlate with higher antibody release. Altogether, these data show that perception of uncanniness in VR evokes mucosal immune responses resembling those related to real contagion threats.