Scientists studying brain process involved in sight have found the visual cortex also uses information gleaned from the ears as well as the eyes when viewing the world.
They suggest this auditory input enables the visual system to predict incoming information and could confer a survival advantage.
Professor Lars Muckli, of the Institute of Neuroscience and Psychology at the University of Glasgow, who led the research, said "Sounds create visual imagery, mental images, and automatic projections.
So for example, if you are in a street and you hear the sound of an approaching motorbike, you expect to see a motorbike coming around the corner. If it turned out to be a horse, you would be very surprised."
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In one experiment they asked the blindfolded volunteers to listen to three different natural sounds - birdsong, traffic noise and a talking crowd.
Using a special algorithm that can identify unique patterns in brain activity, the researchers were able to discriminate between the different sounds being processed in early visual cortex activity.
A second experiment revealed even imagined images, in the absence of both sight and sound, evoked activity in the early visual cortex.
The early visual cortex hasn't previously been known to process auditory information and while there is some anatomical evidence of interconnectedness in monkeys, our study is the first to clearly show a relationship in humans," Muckli said.
"In future we will test how this auditory information supports visual processing, but the assumption is it provides predictions to help the visual system to focus on surprising events which would confer a survival advantage.
"This might provide insights into mental health conditions such as schizophrenia or autism and help us understand how sensory perceptions differ in these individuals", he said.