Mistaking imagination for reality: Congruent mental imagery leads to more liberal perceptual detection

Abstract

Visual experiences can be triggered externally, by signals coming from the outside world during perception; or internally, by signals from memory during mental imagery. Imagery and perception activate similar neural codes in sensory areas, suggesting that they might sometimes be confused. In the current study, we investigated whether imagery influences perception by instructing participants to imagine gratings while externally detecting these same gratings at threshold. In a series of three experiments, we showed that imagery led to a more liberal criterion for reporting stimulus presence, and that this effect was both independent of expectation and stimulus-specific. Furthermore, participants with more vivid imagery were generally more likely to report the presence of external stimuli, independent of condition. The results can be explained as either a low-level sensory or a high-level decision-making effect. We discuss that the most likely explanation is that during imagery, internally generated sensory signals are sometimes confused for perception and suggest how the underlying mechanisms can be further characterized in future research. Our findings show that imagery and perception interact and emphasize that internally and externally generated signals are combined in complex ways to determine conscious perception.

Imagery adds stimulus-specific sensory evidence to perceptual detection

“…The consistent increase in perceptual presence responses for congruent imagery reported here and elsewhere (Dijkstra, Mazor, et al, 2021;Farah, 1989;Moseley et al, 2016) suggests that the brain does not account for self-generated sensory signals during imagery. This observation is in contrast to analogous mechanisms that discount self-generated changes in sensory input caused by action.…”

“…This makes it unlikely that imagery led to a response bias towards reporting stimulus presence, for instance due to demand characteristics. Such a bias in the context of our experiment might have caused participants to blindly respond 'yes' more often during congruent imagery, even in the absence of any changes in sensory processing (Dijkstra, Mazor, et al, 2021). However, if this were the case, it would have led to an increase in presence responses across the full range of stimulus strengths, and therefore also a shift in the guess rate parameter.…”

“…when the same stimulus was simultaneously imagined and perceived, participants were more likely to report perceptual presence Dijkstra, Mazor, Kok, & Fleming, 2021;Farah, 1985Farah, , 1989Moseley, Smailes, Ellison, & Fernyhough, 2016;Saad & Silvanto, 2013). These results have been interpreted as showing that imagined signals are incorporated into perception (Dijkstra, Mazor, et al, 2021).…”

“…Participants. Based on power calculations of a previous experiment with the same paradigm (Dijkstra, Mazor, et al, 2021), we required 34 participants to capture differences in detection criterion and accuracy between conditions. Given that we are interested in slightly more subtle effects in the current study, we decided to recruit 50 participants.…”

“…when the same stimulus was simultaneously imagined and perceived, participants were more likely to report perceptual presence Dijkstra, Mazor, Kok, & Fleming, 2021;Farah, 1985Farah, , 1989Moseley, Smailes, Ellison, & Fernyhough, 2016;Saad & Silvanto, 2013). These results have been interpreted as showing that imagined signals are incorporated into perception (Dijkstra, Mazor, et al, 2021). These latter observations are inconsistent with the brain explaining away or suppressing sensory signals when engaging in imagery, and instead suggest that imagined signals are combined with incoming sensory signals, increasing the probability of reporting external stimulus presence.…”