There’s little more frustrating than frantically searching for your wallet or car keys, only to discover later on you actually picked them up and moved them during the hunt — and don’t even remember doing it.
So what causes our brains to experience that kind of apparent short-circuit?
After a round of recent experiments investigating how we search, Grayden Solman and his colleagues at the University of Waterloo in Ontario, Canada say that the brain systems involved in the task are working at different speeds, with the system responsible for perception unable to keep up.
During their work, published last month in Cognition, Solman’s team created a simple computer-based task that involved searching through a pile of coloured shapes on a computer screen, and volunteers were asked to find a specific shape in a stack as quickly as possible.
“Between 10 and 20 per cent of the time, they would miss the object,” said Solman, even though they picked it up. “We thought that was remarkably often.”
So the team delved deeper. They checked the test subjects’ short-term memories and attention spans to be sure they weren’t simply forgetting what they were looking for or becoming so distracted that they overlooked their target. Neither was the case.
However, the researchers did discover the volunteers’ movements were slower after they had moved and missed their target — indicating that at some level they were aware they’d already found and discarded what they were looking for.
Solman’s team believes the system in the brain that deals with movement is simply running too fast for the visual system to keep up. In other words, while you’re running around trying to find a lost object, your visual system doesn’t have enough time to work out what each object you’re seeing actually is.
“What’s really interesting is the notion that the motor and perceptual system are decoupled. They’re both trying to help you find [the object] but they’re not coordinating,” says Todd Horowitz of Harvard University. “There are implications for social search, such as a doctor looking through an X-ray or [airport security] looking through luggage.”