The Content of Imagined Sounds Changes Visual Motion Perception in the Cross-Bounce Illusion

Tags:

Berger, C. C., & Ehrsson, H. H. (2017). The content of imagined sounds changes visual motion perception in the cross-bounce illusion. Scientific Reports, 7(1). doi:DOI: 10.1038/srep40123

Abstract

Can what we imagine hearing change what we see? Whether imagined sensory stimuli are integrated with external sensory stimuli to shape our perception of the world has only recently begun to come under scrutiny. Here, we made use of the cross-bounce illusion in which an auditory stimulus presented at the moment two passing objects meet promotes the perception that the objects bounce off rather than cross by one another to examine whether the content of imagined sound changes visual motion perception in a manner that is consistent with multisensory integration. The results from this study revealed that auditory imagery of a sound with acoustic properties typical of a collision (i.e., damped sound) promoted the bounce-percept, but auditory imagery of the same sound played backwards (i.e., ramped sound) did not. Moreover, the vividness of the participants’ auditory imagery predicted the strength of this imagery-induced illusion. In a separate experiment, we ruled out the possibility that changes in attention (i.e., sensitivity index d′) or response bias (response bias index c) were sufficient to explain this effect. Together, these findings suggest that this imagery-induced multisensory illusion reflects the successful integration of real and imagined cross-modal sensory stimuli, and more generally, that what we imagine hearing can change what we see.

Authors

Christopher C. Berger1
H. Henrik Ehrsson1

What This Study Is About

Researchers investigated whether the sounds we imagine in our minds can change how we see the physical world. Specifically, they looked at whether imagining a "collision" sound could trick the brain into seeing two objects bounce off each other instead of passing through one another.

How They Studied It

The study involved 72 participants divided into three experiments. Participants watched an animation of two identical discs moving toward each other, overlapping, and then moving apart. This is known as the "cross-bounce illusion" because the discs can look like they either passed through each other or bounced off.

Participants were asked to imagine different types of sounds at the exact moment the discs met:

A "damped" sound (like a sharp "thud" or "clink" typical of a collision).

A "ramped" sound (the same sound played backward, which does not sound like a collision).

No sound at all.

The researchers also tested whether the vividness of a person's mental imagery—their ability to create clear "pictures" or "sounds" in their mind—affected the results.

What They Found

The study found that when people imagined a collision sound, they were significantly more likely to see the discs bounce rather than pass through each other. However, imagining the non-collision (backward) sound had no such effect.

Crucially, the more vivid a participant’s auditory imagery was, the stronger the illusion became. The researchers also ruled out the idea that participants were simply "guessing" or paying less attention; the imagined sound actually changed their sensory perception of the movement.

What This Might Mean

This suggests that the brain integrates mental imagery (what we imagine) with real sensory input (what we see) to create our final experience of reality. It shows that imagery isn't just a weak copy of perception, but a functional tool the brain uses to make sense of the world. For those with aphantasia—the inability to voluntarily create mental images—this raises interesting questions about whether they would experience this specific illusion in the same way.

One Interesting Detail

The illusion only worked when the imagined sound "matched" the visual event. Because a "thud" makes sense for a collision but a backward "whoop" does not, the brain only combined the imagined sound with the visual movement when the two pieces of information felt like they belonged together.

The Content of Imagined Sounds Changes Visual Motion Perception in the Cross-Bounce Illusion

Abstract

Authors

The Content of Imagined Sounds Changes Visual Motion Perception in the Cross-Bounce Illusion

Abstract

Authors

The Content of Imagined Sounds Changes Visual Motion Perception in the Cross-Bounce Illusion

Abstract

Authors

The Content of Imagined Sounds Changes Visual Motion Perception in the Cross-Bounce Illusion

Abstract

Authors

What This Study Is About

How They Studied It

What They Found

What This Might Mean

One Interesting Detail

What This Study Is About

How They Studied It

What They Found

What This Might Mean

One Interesting Detail

Joel Pearson

Merlin Monzel

Adam Zeman

Rebecca Keogh

Martin Reuter

Juha Silvanto

Paolo Bartolomeo

Carla Dance

Jianghao Liu

Fraser Milton