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Abstract:
Our perception is shaped by both sensory inputs and prior expectations, with weaker stimuli being susceptible to influence by expectations of their likelihood. Previous research has demonstrated that the timing of sensory stimulation during the cardiac (Al et al., 2020) and respiratory cycle (Grund et al., 2022, Kluger et al., 2021) can impact perception. The current study aims to investigate how external priors such as stimulus expectations and internal priors, e.g. about cyclic cardiac input, affect somatosensory perception and confidence. Specifically, participants had to indicate whether they perceived a somatosensory near-threshold stimulus and rate their respective confidence level. We manipulated stimulus probability blockwise using cues that indicated either a 25% or 75% chance of a signal, in correspondence with actual stimulus frequency. Signal detection analysis revealed that participants used a more conservative threshold to detect stimuli in the low probability condition. Correct responses that aligned with participants' expectations were rated with higher confidence. Preliminary ECG findings suggest an interaction of stimulus expectation and cardiac phase on both hit rate and perceptual sensitivity, i.e. only when few stimuli were expected, perceptual performance decreased during systole. This is to note as the cardiac phase effect has originally (and so far only) been observed under conditions with a high (not low) ratio of signal trials, yet without overt information about stimulus probability. We are currently analyzing whether this effect is driven by differences in confidence between low and high stimulus expectations.
