Our imagination may affect how we experience the world around us more than was previously thought, for instance, what we imagine seeing or hearing in our head can alter our actual perception, according to new research by a team from the Karolinska Institutet in Sweden.

The finding, published in the journal Current Biology, explores the historic question in neuroscience and biology about how our brains puts together information from all the different senses.

Christopher Berger, doctoral student at the Department of Neuroscience and lead author of the study explained:

“We often think about the things we imagine and the things we perceive as being clearly dissociable. However, what this study shows is that our imagination of a sound or a shape changes how we perceive the world around us in the same way actually hearing that sound or seeing that shape does. Specifically, we found that what we imagine hearing can change what we actually see, and what we imagine seeing can change what we actually hear.”

The study included a series of experiments that used illusions in which sensory information from one sense distorts or changes a person’s perception of another sense. The experiments consisted of 96 healthy volunteers.

The first experiment had volunteers experience the illusion of two passing objects hitting each other rather than passing each other when they imagined a sound at the moment the two objects met.

During the second experiment, subjects’ spatial perception of a sound was biased towards an area where they imagined seeing the short appearance of a white circle. The third experiment involved the participants’ perception of what a person was saying was changed by their imagination of hearing a certain sound.

The results supported perceptually based theories of imagery and suggest that neuronal signals made by imagined stimuli can integrate with signals generated by real stimuli of a different sensory modality to make robust multi sensory percepts.

Scientists believe that the outcomes of the study could be useful in understanding the mechanisms by which the brain is not able to differentiate between reality and thought in certain psychiatric disorders like schizophrenia.

Also, it could be used for research on brain computer interfaces where people who are paralyzed can use their imagination to control artificial and virtual devices.

Professor Henrik Ehrsson, the principle investigator behind the study said:

“This is the first set of experiments to definitively establish that the sensory signals generated by one’s imagination are strong enough to change one’s real-world perception of a different sensory modality.”

Written by Kelly Fitzgerald