Scientists have discovered why a ‘visual ear’ phenomenon lets some people ‘hear’ silent gif images such as the famous ‘skipping pylon’ animation. A new study has suggested the remarkable ‘synaesthesia-like effect’ is caused by interference between areas of the brain responsible for processing sight and sound. Normally, these two parts of our brains do not work together. But they may ‘cooperate’ in people who are able to hear silent images thanks to a ‘visually-evoked auditory response’, which is also known as VEAR or visual ear.
Researchers from City University in London found that musicians are more likely to experience visual ear because their ‘training may promote joint attention to both the sound of music and the sight of the coordinated movements of the conductor or other musicians’. Dr Elliot Freeman, principal investigator on the study and a senior lecturer in psychology at the university, said: ‘We already knew that some people hear what they see. Car indicator lights, flashing neon shop signs, and people’s movements as they walk may all trigger an auditory sensation. ‘Our latest study reveals normally-occurring individual differences in how our senses of vision and hearing interact. ‘We found that people with ‘visual ears’ can use both senses together to see and also ‘hear’ silent motion, while for others hearing is inhibited when watching such visual sequences.’ People who experience synaesthesia often reporting getting a sense of colour from music, letters or numbers. Visual ear appears to be the most common form of synaesthesia, with as many as 20% of people reporting some experiences of it compared to 4.4% for other types.
To understand the phenomenon, researchers applied a weak electrical current to participants’ scalps using a technique called transcranial Alternating Current Stimulation (tACS). This allowed them to explore how visual and auditory parts of the brain interact. The researchers found that stimulating auditory brain areas significantly reduced hearing performance but improved visual performance in people who did not have visual ear. This was also true in reverse, with the stimulation of areas responsible for seeing reducing participants hearing ability. The results indicate that brain areas responsible for the two senses inhibit each other’s performance. However, the same effect was not seen in people who experience visual ear, suggesting the brain regions were actually cooperating with each other. Dr Freeman added: ‘We were also interested to find that, on average, participants with visual ear performed better on both visual and auditory tasks than those without. Perhaps their audio-visual cooperation benefits performance because more of the brain is engaged in processing visual stimuli. ‘Such cooperation might also benefit musical performance, explaining why so many of the musicians we tested reported experiencing visual ear.’
Published by Jasper HamillThursday 28 Mar 2019 10:11 am on METRO News.