A computational account of perceptual uncertainty in paradoxical heat sensation

Paradoxical heat sensation (PHS) is conventionally described as the perception of warmth elicited by innocuous cooling, yet the qualitative nature of this experience remains largely uncharacterised. To describe potential differences in how PHS is perceived, we compared 2 a priori profiles: "true perceivers," who experience PHS as a clear, warm percept, and "unsure perceivers," who experience it as an ambiguous sensation. Seventy-five healthy adults (21-80 years old) performed a perceptual decision-making task designed to elicit PHS by manipulating the thermal contrast between warm and cold temperatures. To test the PHS experience across the lifespan, we applied hierarchical multivariate Bayesian modelling in which perceptual choices, response times, and confidence ratings were expected to vary systematically across the 2 hypothesised perceptual profiles. At the group level, behaviour was best accounted for by the unsure perceiver model, indicating that PHS is most often an uncertain experience, rather than a categorical misperception. Both profiles were present across individuals, demonstrating substantial interindividual variability in perceptual patterns. Older adults reported PHS more frequently, and at lower thermal contrasts, but their perceptual profiles did not differ from those of younger participants. This suggests that ageing increases the likelihood of experiencing PHS without changing its qualitative nature. These findings show that PHS is a heterogeneous perceptual phenomenon defined by variability in certainty and subjective quality across individuals.