Because there’s too much information out there for us to process all at once, we have to selectively attend to some things at the expense of others. Indeed, psychologists have spent a lot of time examining how we select certain things for preferential processing – colours, movement, whole objects and so on. But David Melcher at Oxford Brookes University and his colleagues wanted to know: how does what we’re focused on at the centre of our attention, affect the way we process things elsewhere, out of the corner of our eye?
Seven volunteers staring straight ahead first concentrated on either the red or green dots that were moving on the left side of a computer display (the red ones all moved up, the green ones moved down). They had to spot when the colours changed slightly.
Next they had to focus on a load of randomly moving (bouncing all over the place) red and green dots on the right side of the screen, and look out for a brief period of coherent motion, when a fraction of the dots would suddenly all move together, either to the left or right. This can be tricky, and their task was to say what direction the fraction of dots moved in – leftward or rightward?
Now this is the important part: to help them, the direction of this brief, coherent motion among the dots was actually revealed earlier, when they were busy looking to the left side of space, waiting to spot the colour change there. It was revealed by a burst of coherent horizontal motion among the dots on the right-hand side, that happened far too quickly for them to consciously see it, but which predicted the direction of the later burst (a kind of subconscious giveaway).
Crucially, Melcher found that whether this earlier subliminal giveaway helped or not depended on whether it was made up of the same colour dots that the participants were busy looking at over on the left. When it was the same colour, the participants obviously tuned into it on some level (even though their attention was focused to the left), because it then doubled their ability to detect the direction of the later burst of horizontal motion they had to look out for.
The take home message? If we’re focusing on red in one region of space, then we also preferentially process unrelated red things in another part of space – even things we’re not conscious of, and which are irrelevant to the task we’re currently busy with.
Melcher, D. Papathomas, T.V. & Vidnyanszky, Z. (2005). Implicit attentional selection of bound visual features. Neuron, 46, 723-729.