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

DOI: 10.1038/srep40123
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

Overview/Introduction

Have you ever wondered if what you imagine hearing can influence what you see? This intriguing question was the focus of a recent study exploring the connection between imagined sounds and visual perception. The researchers investigated whether imagining specific sounds could alter the way we perceive motion, using a phenomenon known as the "cross-bounce illusion." This illusion occurs when a sound is played as two objects pass each other, making them appear to bounce off one another instead of crossing paths.

Methodology

The study involved three experiments with a total of 72 participants. In the first experiment, participants were asked to imagine hearing a "damped" sound (typical of a collision) or a "ramped" sound (the same sound played backward) as two discs moved across a screen. The researchers wanted to see if imagining these sounds would affect the perception of the discs bouncing. In the second experiment, the sounds were actually played to participants instead of imagined. The third experiment tested whether imagining sounds influenced participants' attention or response tendencies.

Key Findings

  • Imagined Sounds and Visual Perception: Imagining a damped sound increased the likelihood of perceiving the discs as bouncing, while imagining a ramped sound did not have the same effect.
  • Vividness Matters: Participants who reported more vivid auditory imagery experienced a stronger illusion, suggesting that the clarity of imagined sounds plays a role in altering visual perception.
  • Real vs. Imagined Sounds: The effect of imagined sounds on perception was similar to that of real sounds, indicating that imagined auditory stimuli can integrate with visual stimuli to change perception.
  • Attention and Bias: The study found no evidence that changes in attention or response bias could explain the observed effects, supporting the idea that the illusion reflects genuine multisensory integration.

Implications

These findings suggest that our imagination can influence how we perceive the world around us, highlighting the power of multisensory integration. This research could have practical applications in areas like virtual reality, where imagined sounds might enhance user experiences by altering visual perceptions. It also opens up new avenues for exploring how mental imagery can be used in therapeutic settings to modify perceptions and behaviors.

Limitations

While the study provides compelling evidence for the role of imagined sounds in altering visual perception, it primarily focused on a specific type of illusion and sound. Future research could explore a broader range of sensory stimuli and contexts to better understand the full scope of multisensory integration.
In conclusion, this study sheds light on the fascinating interplay between what we imagine and what we perceive, suggesting that our minds have a powerful influence on how we experience the world.