Experts look into gap between sight and understanding


WHEN WE look, what do we really see?

While our eyes look at objects and our brain interprets and represents what we perceive, a mismatch between the two – caused by physiological conditions and natural perception problems – means we may not actually see what is in front of our very eyes.

Our brain recognises objects by taking the features we observe and fitting them together to make a representation, according to Dr Rama Chakravarthi, lecturer in psychology at the University of Aberdeen, who addressed a session at the science festival on how we could look but not see.

Occasionally, our brain is unable to fit together the visual information to make sense of what we are looking at. For example, we cannot readily identify an object surrounded by visual “clutter” such as a familiar person in a crowd.

Sometimes, when concentrating on a task, we fail to notice an unexpected yet highly visible object. In a classic perception experiment, subjects were asked to count the number of times a team pass a basketball. So engrossed were the observers that they failed to notice a conspicuous, out-of-context object that walked in front of them – a person in a gorilla suit. Why we filter visual information is not understood – it may be related to our mental workload and the attention required to complete tasks.

Understanding how the brain processes vision has implications for the visually impaired or those with reduced perception, said University of Oxford undergraduate Samantha Mansell.

After a stroke to the right side of the brain, 80 per cent of survivors act as if the left-hand side does not exist, said Dr Monica Harvey, reader in psychology at the University of Glasgow. A stroke patient with the condition will eat food only on the right side of a plate and leave the left side alone, as their condition causes them to be unaware of any food on the left.

Different areas of the brain can be affected by a stroke – lower parts governing perception might be damaged, whilst the upper regions concerning actions could be less so. Dr Harvey has found that when patients repeatedly interact with items on their left- hand side, they increase their perception of objects in this area and are less likely to ignore them.

Becca Wilson is a British Science Association media fellow at The Irish Times