Your Brain Sees Even When You Don't

The unconscious processing abilities of the human brain are estimated at roughly 11 million pieces of information per second. Compare that to the estimate for conscious processing: about 40 pieces per second.*

Our conscious processing capacity isn’t insignificant, but clearly it’s just a retention pond compared to the ocean of the unconscious. And more and more research is uncovering abilities of the unconscious that defy reason. Two recently published studies on how the brain “sees” illustrate the point--the first one is cool, the second borders on incredible.

The first, published in the journal Psychological Science, wanted to find out if the brain can track visual targets even when the eyes are duped into believing the targets aren’t there. Researchers at the Brain and Mind Institute at the University of Western Ontario exposed participants to an optical trick known as the “connectedness illusion” that causes viewers to underestimate the number of circles (targets) on a screen.

Two groups of circles are presented, one group on the left side of a screen and one on the right.  The circles in one group are connected to tiny lines, but the circles aren’t connected to each other. In the other group, the circles are connected to each other via the lines.  What consistently happens is that our eyes perceive fewer circles in the connected group than in the disconnected group, even though the number of circles in both groups is exactly the same.

The connectedness illusion is a proven way to trick the eyes, and it worked like a charm in this study: participants didn’t see all of the connected circles. But when they were given a task to “act” on the targets, researchers found that participants shifted from visual “seeing” to what you might call brain-sight. They were able to strategically plan actions that included all of the targets even though they didn’t visually perceive them.

The reason seems to be that visual processing operates along two paths. The first is the one we’re most familiar with—how we visually perceive the world. The second is what our brains are unconsciously up to while we’re focused on merely “seeing."

Said lead researcher Jennifer Milne, a PhD student at the University of Western Ontario:   "It's as though we have a semi-autonomous robot in our brain that plans and executes actions on our behalf with only the broadest of instructions from us."

That was cool, but the next study--published in The Journal of Neuroscience--flirts with the incredible. Researchers wanted to know if the brain can “see” someone else's actions even when the ability to visually see has been destroyed.

Cortical blindness refers to the loss of vision that occurs when the primary visual cortex no longer functions, generally as the result of injury. There’s no longer an ability to visually perceive the world in the sense with which we’re most familiar (even though the eyes still technically work), but that doesn’t necessarily mean the brain no longer sees.

In this study a patient with full cortical blindness could still react to another person's gaze. While in an fMRI machine, the patient was exposed to gazes directed at him and gazes directed away from him. On the face of it, neither should matter. His visual cortex couldn’t perceive any sort of gaze. But the brain scan indicated that another part of his brain definitely could.

The patient’s amygdala, the brain area associated with figuring out whether external stimuli is a threat, showed a distinctly different activation pattern when the gaze was directed at the patient than when directed away from him.

In other words, it didn't matter that his visual cortex couldn't catch the gaze—another part of his brain did regardless.

Exactly what's going on here isn't known, but there's a certain intuitive sense about the reaction even as it defies conscious reason. Our brains are adaptive marvels, and adapting around impediments to survival is essentially what our magical cranial clay does. If one system goes down, in this case external visual processing, it makes adaptive sense that another system would fill the gap (how that happens--well, that's the question).

We are only touching the jagged frozen tip of the iceberg with studies like these, and the second one in particular shows just how much we don't know about the brain's unconscious mojo. But we're learning more all the time, and piece by quixotic piece, the puzzle is only getting more intriguing.

*For more on conscious versus unconscious brain processing power, check out Timothy Wilson's excellent book, Strangers to Ourselves.

David DiSalvo's newest book, Brain Changer, is now available for pre-order on Amazon and Barnes and Noble. It will hit store shelves on November 12.

Posted on August 11, 2013 .