EXPRESS: When illusion rivals reality. Investigating error detection and the role of working memory resources in the Vanishing Ball Illusion.

In the vanishing ball illusion (VBI), a magician feigns throwing a ball, and spectators report seeing it rise into the air, even though it never leaves the performer's hand. Although many studies have investigated factors that can modulate this illusion, none have examined the extent to which participants can detect this anticipatory error, or whether susceptibility to the illusion and this potential detection depend on available executive resources. In the present study, error detection was assessed by comparing the confidence in the perceptual experience of participants susceptible to the VBI (N = 64) with that of participants exposed to a real throw (N = 64). Moreover, working memory resources were manipulated by asking participants to memorize either two (low load) or four (high load) cross positions presented in a 3 × 3 grid. Contrary to our hypothesis, working memory resource availability did not significantly affect susceptibility to the VBI. Moreover, participants' confidence in detecting an error did not differ between those experiencing the VBI and those observing a real throw, and this lack of error detection was independent of available working memory resources. Our findings suggest that the illusory ball is interpreted and trusted as if it were genuine bottom-up information (i.e., a real throw). We discuss the mechanisms underlying this illusion that may account for the absence of error detection, focusing in particular on the roles of source monitoring and the automatization of perceptual simplification processes.