Another day and some more psychology. In the Blink of an Eye involved four talks all revolving around vision and attention. “The whole of life lies in the verb seeing,” Telihard De Chardin, it is true that sight would be the sense most would prefer to keep, above say smell or touch, should one be taken from us. But is this cherished sense infallible, and how much does it depend on attention?
We can find out exactly which parts of the brain compute images by mapping loss of vision to areas of brain damage, such as that done by Holmes in the first World War, or more simply by mapping waves of activity by fMRI in response to the movement of a visual stimulus. Now to look at the contribution of attention to perception. The study of inattentional blindness looks at how people can fail to see objects right in front of them because their attention is elsewhere. For instance a rather famous experiment where people are asked to count the number of passes by the white basketball players and fail to notice a gorilla walk out into the middle of the screen, look at the camera, and walk off. Ignoring the distractions was required to complete the task, after all you have only a finite amount of attention available as a resource, and so you don’t waste attention on the gorilla as an unexpected object. If you are not convinced, how about trying this demonstration of inattentional blindness from the BBC. So maybe there is no conscious perception without attention, but then certain things like your own name would seem to be noticed automatically without the consciousness need for attention. In fact if you are directing attention towards a particular task, say identifying pictures of animals on a screen whilst ignoring the pictures of fruit, you would identify unexpected words presented as part of that study only if they are examples of a type of animal e.g. TIGER. Words of fruit, GRAPES, or those on the same theme as the attention task whilst not actually being an example of that category, such as ZOO or FARM, would be ignored and not recalled at the end of the task. Clearly this type of blindness is more complex than simply not seeing that which is not expected.
What other tricks can we play on our brains, or rather do our brains play on us? How about a picture of a crowded street, you have to find the baby in the picture without moving your focus point from a cross in the middle of the scene. It is almost impossible because of the “crowding effect”, but if you were to take the crowd away all of a sudden it is very easy to see the infant without having to move your gaze. The image is processed by your brain, identifying all the features (lines, colours motion, orientation, depth) and combining that information into an integrated image that you can identify. What happens in a crowded area is that areas of the image get grouped and all the features processed together; the combination of that information gives you a jumbled image that can no longer be identified. Instead our attention must be moved to concentrate on smaller parts of the image to scan for what we are looking for, there is too much information to allow perception without attention. This is actually how our world is perceived, not a seamless full definition image but a scene that has gaps that are only filled in if our attention can be draw to them or if we intentionally scan for an object.
So what happens if our attention is not drawn to an area? Visual neglect exists as a consequence of damage to the visual processing areas of the brain such as that caused by stroke. Vision is separated and processed by both sides of the brain, data from the right hand side of the visual field is processed on the left of the brain and vice-versa. If there is damage to this area on one side of the brain hemispatial, one-sided, neglect happens where individuals can no longer see anything on the opposite side of the visual field. Not only do they not see anything there but they forget to look and without attention there is no perception. Individuals will leave half plates of food because they just cannot see it, however they would be able to point at an object in the blind area should they be asked to find it. Whilst there is currently no recognised effective treatment if an individual can re learn perception by directing their attention to point at objects neglect of an area of the visual field can be neglected.
I shall leave you with an attention themed thought “You can become blind by seeing each day as a similar one. Each day is a different one, each day brings a miracle of its own. It’s just a matter of paying attention to this miracle.” Paulo Coelho
Beckie Port is a Cancer Research UK funded PhD student in the School of Cancer Sciences, University of Birmingham. You can follow her on Facebook or @beckieport. Beckie is attending the festival as part of a Scientific Public Engagement Award from the University of Birmingham and the Festival Student Bursary Scheme.