Disentangling perceptual and response biases: The act of detecting a stimulus contaminates measures of conscious experience

A central challenge in consciousness research is determining whether observers have a conscious experience of a stimulus. However, present/absent detection judgments are often biased by contextual factors, making it difficult to isolate conscious perception from non-perceptual influences. Traditional psychophysical methods struggle to disentangle these components. To address this, we conducted in-person experiments (N=505) in which participants detected and reproduced dim and absent stimuli under three contextual manipulations: attentional cues, asymmetrical base rates, and payoff schemes. Using a reproduction task together with a Hurdle-Gaussian model, we quantitively decomposed reproduction responses into a perceptual continuous contrast component and a non-perceptual “hurdle” component. We found that statistical priors (base rate) and reward structures (payoff) induced non-perceptual shifts in the reproduction hurdle, whereas attentional cues selectively shifted the continuous contrast component, consistent with changes in conscious experience. Critically, comparing conditions with and without intermixed detection trials revealed that the presence of a detection task contaminates reproduction reports with non-perceptual criterion effects. This highlights the need for caution in using and interpreting results that rely on detection judgements, even when combined with subjective measures like reproduction, especially given the central role that detection tasks play in consciousness research.