The Attentional Spotlight

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The experience of ‘looking out of the corner of the eye’ using peripheral vision is commonplace but it conceals a unusual fact about attention. That is that we probably spend a lot more of our time than we might imagine with our ‘mind’s eye’ looking in a different direction to our eyeballs.

Eye direction normally coincides with where attention is directed but it is such an important social signal that disguise is sometimes necessary. Take these for instance:

  • People in close proximity like rail commuters who can watch each other by adopting a fixed gaze and letting their attention wander around the visual field.
  • Parents keeping tabs on their children out of the corner of their eye while looking at their conversational partner.
  • Skilled sports people hiding their intended passes or moves by using their peripheral vision rather than looking directly.

Although this phenomenon is a common everyday experience, the way attention moves around the visual field has been a tricky one for scientists to examine. Up until the 1970s psychologists  found it very difficult to prove experimentally that attention could move without the eyes.

Then an explosion of experiments in the 70s provided just the evidence scientists had been waiting for. These led to one of the most famous metaphors for visual attention: the attentional spotlight. This is the idea that our attention moves around our field of vision so that the things falling within its beam are processed preferentially. Attention can be both consciously directed and hijacked by unconscious processes so that, for example, we can avoid getting hit by buses.

Attention moves faster than the eye

One classic experiment that finds the ‘attentional spotlight’ zipping away from eye direction was carried out by Professor Michael Posner and colleagues at the University of Oregon (Posner, Snyder & Davidson, 1980).

Across a series of different conditions they had participants press a button as quickly as possible when they saw a light appear. In some conditions participants were given a little hint about where the light was going to appear, either they saw:

  • an arrow in the centre pointing left or right,
  • or a box at the edge indicating where the light would appear.

These hints were provided just a fraction of a second before the flash of light so people didn’t have time to move their eyes (this was checked using electrooculography). The question researchers were interested in was whether people were faster to respond to the light when given a clue about its position, compared with no clue.

What they found was that people were about 50 milliseconds (one-half of a tenth of a second) faster to detect the light when given a clue than not — a significant advantage. What this suggests is that something other than the eyes, which don’t have time to shift, has moved to the area where the light was expected.

From experiments like this Posner and others argued that it is our attention moving around the visual field, often remarkably independent of our actual gaze direction. Indeed even if we’re looking directly at something, and when we don’t expect to see it, we’re no more likely to notice it than if it appears on the edge of our vision (Posner (1980). This is a fact oft-used by magicians (see the psychology of magic, especially part 3 cogntive illusions).

It appears that attention can be likened to a spotlight roving across our vision like a virtual eye, just picking out the things in which it is interested; it’s not as attached to where we point our eyes as we might imagine.

Turning off the spotlight

Just how important the attentional spotlight is to our everyday functioning is made all the more obvious by patients who seem to ‘ignore’ one half of their visual fields. After suffering brain damage, usually to the right hemisphere, they start ignoring or neglecting everything on the left (because of the way the right hemisphere processes information from the left visual field, and the left hemisphere from the right visual field).

Despite both eyes being physically functional, because of the damage to the visual processing centres, it’s as though the attentional spotlight can’t travel over to the left hand side. Technically they can see to the left but crucially they don’t notice anything. People with this problem might shave only one side of their face or only eat half of the food on their plate.

Is attention really like a spotlight?

The attentional spotlight theory isn’t the only metaphor to be used to describe the way attention moves across the visual field. One popular cousin of the spotlight theory is the zoom-lens metaphor. Rather than a beam of attention of a set size, Eriksen and St. James (1986) argue that we zoom in and out depending on the task. There is also evidence, such as LaBerge (1983), which supports this model.

Like many metaphors, though, it’s not wise to take the attentional spotlight or the zoom-lens too literally. Subsequent findings examining the details have questioned several aspects of these theories, but there are two main objections to both:

  1. Studies suggest that attention can be split between two locations: this doesn’t easily fit with the idea of a single attentional ‘beam’ or ‘lens’.
  2. Research has shown that we can actually process visual stimuli outside the spotlight/zoom-lens quite thoroughly. Similarly patients with hemispheric neglect have been found to process visual information presented to their ‘neglected’ side.

Although there are problems with the attentional spotlight and zoom-lens as metaphors, they still provide a useful insight into how our attention can move independently of the eyes. The evidence also scientifically confirms the everyday experience of fixing the gaze and still being able to ‘look around’.

[Image credits: orangeacid & Paul Colacino & uBookworm]

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Published: 23 March 2009

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