Nearly all of us can fold our clothes or pour a glass of water without fail. Fewer can safely catch a Frisbee, and nearly no one can catch a fly with a pair of chopsticks. Chances are, you fall somewhere on this spectrum, as our visual systems are universally tied to our motor ones. Now science argues it’s more than just commonplace; it’s hard-wired from birth.
Hand-Vision, Not Hand-Eye
Catching a fly with a pair of chopsticks is a party trick (or a lesson in discipline, if you’re Mr. Miyagi). The truth is, these two systems works unconsciously in the background at all times throughout the day. Your brain is so good at syncing the movement of your body with the random patterns of light smashing against your retina that you don’t even know you’re doing it, which helpfully frees you up to concentrate on other, more important things.
This hard-wiring was just discovered by researchers at the University College London, who recruited 52 people for a set of games that put their reflexes and ability to concentrate to the test. Since our visual systems aren’t very good at staying on task (read: humans are easily distracted), the experimenters sought to understand whether prompting subjects with disruptive stimuli during a required task would impair their automatic responses. Interestingly, it didn’t.
The subjects played three games. The first game involved using a set of robotic arms to move a cursor on a screen over to a desired target. Subjects had to affix their gaze at a mark in the screen’s center, which the team measured with eye-tracking technology. When participants moved the cursor, by design it would occasionally jump to the wrong target, so they had to correct it. This was paired with a light on either side of the targets that would flash at random — the experiment’s distraction. Think of it not as hand-eye coordination, but “hand-vision coordination.”
If the visual and motor systems weren’t hard-wired the results would have been chaos, with reaction times suffering because of the greater “noise.” But that’s not what the team observed. Even with the flashing lights to misdirect the subjects, their unconscious systems took over and guided their movements based on what they saw.
"The first experiment showed us that we react very quickly to changes relating to objects directly under our own control, even when we are not paying attention to them," explained lead author Dr. Alexandra Reichenbach in a statement. "This provides strong evidence for a dedicated neural pathway linking motor control to visual information, independently of the standard visual systems that are dependent on attention."
Subjects didn’t rely on their focus and concentration, in other words, to correctly move the cursor. If they had, the distractions would’ve overwhelmed them. What they were really using was their built-in system of hand-vision coordination. In the same way we instantly recognize faces based on simple, abstract patterns, our brains are constantly pulling the strings to make our bodies move in sync with what we see.
Finding a Larger Purpose
To push the study further, the team’s second experiment involved a light that changed in brightness, adding another element of uncertainty and disruption into completing the desired task. The third experiment added more targets and cursors, both of which jumped at random. Still focused with eyes straight ahead, subjects had to correctly maneuver the cursor onto a single target despite other dummy targets and cursors flooding the periphery. Still, the unconscious system won. Response times were noticeably slower, but far faster than any conscious effort could produce.
"These results provide further evidence of a dedicated 'visuomotor binding' mechanism that is less prone to distractions than standard visual processing," Reichenbach said.
This should make evolutionary sense. Consider the fatal hazard of not noticing predators hidden among the tall grass, or a mugger looking to land a cheap shot before swiping your valuables. In both cases, your ability to sense danger and react bubbles up in an instant from your natural fear centers in the brain’s amygdala. How you react — running, freezing, or fighting — is another matter, but the fact you reacted at all demonstrates that visuomotor binding. Without it, you’d be short a phone and wallet, or worse.
Moving forward with the research has Reichenbach and her colleagues questioning visuomotor binding in schizophrenia patients. A mental disorder often characterized by absent self-control, schizophrenia may manifest itself neurologically in the same way as, say, patients with prosthetic limbs who struggle to get their brain and body in sync again.
"If someone does not automatically link corresponding visual cues with body motion, then they might have the feeling that they are not controlling their movements,” Reichenbach said. “We would need further research to confirm this, and it would be fascinating to see how schizophrenia patients perform in these experiments."
Source: Reichenbach A, et al. A Dedicated Binding Mechanism for the Visual Control of Movement. Current Biology. 2014.