3.1. Results from experiment one (OSF including preregistration: https://osf.io/v9khb/) indicated that interoceptive (cardiac) signals can guide expectations of exteroceptive (auditory) stimuli and that attention towards internal signals modulates interoceptive predictive mechanisms. These effects were unrelated to subjective experience as measured by individual differences in interoceptive accuracy, sensibility and awareness. This could be because the two alternative forced choice method of assessing interoceptive ability (used in experiment one) may not accurately determine task performance and subjective experience, as a result of individual differences in the timing of heartbeat sensations. We aim to overcome this issue by determining individually adjusted cardio-audio delays a priori (using the method of constant stimuli (MCS)), which will be implemented into the second part of the experiment by adjusting the delays used for the perceived synchronous and perceived asynchronous conditions. This should more accurately determine interoceptive ability, therefore allowing us to analyse the relationship of subjective experience with interoceptive predictive mechanisms. 3.2. Additionally, we will compare ERP differences in response to sounds presented at different cardio-audio delays (during the MCS). This will allow us to determine whether there are neural differences depending on the timing of an individual's perception of their heartbeat. We predict a reduced auditory potential at the interval which results in the perception of cardio-audio synchrony, in comparison to intervals resulting in the perception of cardio-audio asynchrony. This would support predictive coding accounts as the perception of cardio-audio synchrony is a result of cardiac-driven predictions of a sound, therefore the delay which results in cardio-audio synchrony will exhibit less prediction error than the delay not engaged in cardiac driven predictions. We expect the opposite pattern when comparing heart-evoked potentials after the presentation of sounds (no auditory stimulus) as a result of expecting a sound on the basis of the heartbeat, resulting in increased prediction error in the absence of a sound.