How participants create illusory experiences to help experimenters

Across four studies (total n = 2,042, two preregistered, one partly preregistered), we investigated the degree to which experiences in psychological experiments may arise from participants controlling their experience to satisfy their goals, i.e., phenomenological control (PC). Trait PC has previously been shown to predict some experimental measures of changes in experience when demand characteristics are not controlled. Here, we investigated the reach of PC as a demand effect by contrasting relationships between Phenomenological Control Scale scores (PCS; a test of direct imaginative suggestion) and effects presumed to either be sensitive to beliefs (visually evoked auditory response or vEAR; tingling in the scalp or ASMR) or insensitive to beliefs (the Müller Lyer illusion; the vertical-horizontal illusion). PC accounted for much of the effect for the posited belief-sensitive effects but not for the classic visual illusions (Study 1). This pattern of results remained after controlling for context effects (Study 2) and measurement differences across procedures (Study 3). Finally, we present the first causal evidence that the two established psychological effects which are predicted by PC (vEAR and ASMR) can be modulated by participants high in PC in accordance with demand characteristics delivered by direct suggestion (Study 4). PC may account for the effects of psychological experiments when an effect is sensitive to belief, but not where it is not. This presents a previously unrecognised threat to validity in psychology experiments analogous to that of placebo effects in medicine.