The research is beginning to reveal where in a scene people direct their attention as well as what kinds of changes are more noticeable.

"It all boils down to contrast," he says. "So colour or orientation contrast; luminance contrast in terms of light and dark things that pop out."

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Their test has also revealed some more specific points about what types of contrast are more obvious to us. We are more likely, for example, to spot that an object has been removed from a scene than if it has changed colour.