There's a storm of sensory information out there in the world but your brain can only process so much at once. To cope, it's armed with an attentional spotlight that allows you to focus on what you're interested in and ignore the rest.
This metaphorical spotlight is a clever piece of kit – its beam needn't be restricted like a torch to one region of space at time. It's rather more like a highlighter pen on a page – flagging up any objects that match the features, such as size and colour, that you've decided you're interested in. This is your mindset, or 'attentional set' as psychologists call it. The trouble is, what happens when a threat appears outside of your attentional set? When it comes to driving, Steven Most and Robert Astur report the consequences can be disastrous.
Fifty-six participants navigated an urban route on a driving simulator. At each cross-roads there was a sign featuring blue and yellow arrows, and the participants were told to always follow the blue arrows or always follow the yellow arrows. This instruction fixed their 'attentional set'. Then suddenly at the tenth cross-roads, a blue or yellow motorbike swerved into their path.
Crucially, for half the drivers, the bike was blue when they'd been instructed to follow yellow arrows, or vice versa. That is, the bike was inconsistent with their attentional set. These drivers braked 186ms slower than the drivers for whom the bike colour and relevant arrow colour matched. Moreover, 36 per cent of them collided with the bike compared with just 7 per cent of the drivers for whom the bike and arrows matched.
“Had this been a real situation instead of a simulation, the consequences of these collisions could have been life-threatening”, the researchers said. “It appears that attentional set wields substantial power even when the behavioural urgency of a stimulus might be predicted to override, or 'short-circuit', top-down attentional control”.
Most, S.B. & Astur, R.S. (2007). Feature-based attentional set as a cause of traffic accidents. Visual Cognition, 15, 125-132.
Link to more detail via university press release.