There are certain things in the environment that grab our attention – loud noises, flashes of light and rapidly moving objects.

These are all reasons why we are likely to spot ambulances dashing towards us and mean that we can act in time to get out of the way.

However, there are also more subtle things that attract attention when we are surrounded by a more mundane environment.

Certain properties of the world are more SALIENT to our visual system than others.

These are: changes in colour (e.g. red to green); changes in contrast (e.g. sharp to blurred ); changes in intensity (e.g. bright to dim); changes in orientation (e.g. vertical to horizontal).

These are some of the reasons why human EYES are so effective in capturing attention – the iris is coloured, there is a sharp contrast between the pupil, iris and sclera and there is a change in orientation of the contrast boundaries around the eye.

In our environment there are often many other things that share these features that compete for our attention e.g. traffic signs, advertisements, bright clothing. As we look around some of the things we look at are influenced by this change in VISUAL SALIENCY.

When we look at pictures, we can break them down into their constituent properties. Below are two photograph and their associated VISUAL SALIENCY maps.

These maps can predict where you will look in a scene on the basis of visual saliency. The little “1″ on the maps above show the most salient point. The following 9 most salient points can be found by following the red line around the photos.

The model doesn’t get it exactly right as we are able to over-power these properties and CHOOSE to look where we want but when we first see pictures we are more likely to look at the salient regions, before we’ve got the gist of what is going on.

At Sheffield, we’ve recently published a paper which investigates whether people with autism and Aspergers look at scenes in the same way.

In the journal Neuropsychologia, we have shown that people with autism also show this bias for looking at salient regions when they first see scenes (Freeth, Foulsham & Chapman, 2011).

However, we also showed that both typically developing viewers and viewers with autism and Aspergers are more strongly drawn to looking at social aspects of scenes – the people – even when they are not “visually salient”.

This finding is very surprising as it was previously thought that people with autism wouldn’t be drawn to look at people.

However, there was also an important difference: participants with autism/Aspergers were significantly slower to look at people’s head and faces when they were looking at scenes than the typically developing participants.

It seems that the fast-track mechanism to attend to other people is absent in people who have autism/Aspergers.