How the Brain Handles Conflicting Sensory InputWhen the brain receives conflicting sensory information, it figures out what it perceives based on information from other senses and from past experience. The result is that what you see is not always what your brain thinks you see. A study from Vanderbilt University and Korea University in Seoul investigated how other senses can influence the eyes. The study showed that, when looking at a different image with each eye, the brain gives equal time to each image. However, when additional sensory information corroborates what one eye sees, the brain gives more attention to what it perceives from multiple senses.

The researchers wanted to investigate how the brain integrates what it sees with supplementary information from other senses. They began by considering a common sensory trick: if a person sees one flash of light and hears two beeps in close succession, he might incorrectly perceive two flashes, instead of just one. The researchers created their own sensory conflicts using a technique tell binocular rivalry. Binocular rivalry involves presenting different images to each eye. The brain then attempts to resolve the conflict between the images.

For this experiment, the researchers showed participants a scrolling musical score on one side of the binocular rivalry and moving contours in the other. The participants pressed one button when the contours dominated their vision and another when the musical score dominated. The results for this test were as expected. The participants alternated between “seeing” each image and each image was dominant for a roughly equal period.

Next, the researchers introduced music into the experiment. The participants watched the same images while listening to music through headphones. The music sometimes corresponded to the musical score, but sometimes it did not. When the participants listened to the music, the image of the musical score dominated their vision for longer periods compared to the moving contours. Participants who were musicians reported seeing the musical score for even longer periods when the score represented the music they heard. For non-musicians participants, there was no difference in what they saw when the score matched the music being played. They reported seeing the score for longer as long as they heard the music.

“What this tells us is that the kind of information the brain uses to interpret what we see around us includes abstract symbolic input such as music notation. However, this kind of input is only effective while an individual is aware of it,” stated director of the study Randolph Blake, Centennial Professor of Psychology at Vanderbilt.

This research is published in the Proceedings of the National Academy of Sciences.

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