Blind to change. Recent experimental psychology studies indicate that “we see far less than we think we do.” Our subjective experience of seeing a rich, full visual scene of the world at all times is just an illusion; we take in only salient details and rely on extrapolation from memory or imagination to fill in the rest. Neurological probes have recently demonstrated that the same neurons activate when viewing a scene in the mind’s eye as when viewing it outwardly, suggesting the same conclusion from a different direction. Daniel Dennett proposed this in his 1991 book Consciousness Explained, observing how computationally inefficient it would be to store the entire elaborate picture in short-term memory. Instead, we log what has changed and assume the rest has remained the same. Implications of the potential for error in this model of perception include calling into question the validity of eyewitness testimony, for example. Some of the further reaches of extrapolation from these findings pose epistemological challenges about what we really know about the world “out there.”

Back in 1992, Kevin

O’Regan, an experimental psychologist at the French National

Centre for Scientific Research (CNRS) in Paris put forward

what later became known as his “grand illusion” theory. He

argued that we hold no picture of the visual world in our

brains. Instead, we refer back to the external visual world as

different aspects become important. The illusion arises from

the fact that as soon as you ask yourself “am I seeing this or

that?” you turn your attention to it and see it.

According to O’Regan, it’s not just our impression of richness

that is illusory, but also the sense of having control over what

we see. “We have the illusion that when something flickers

outside the window, we notice it flickering and decide to move

our eyes and look,” says Susan Blackmore of the University of

the West of England, who supports O’Regan’s views. “That’s

balderdash.” In fact, she says, we are at the mercy of our

change detection mechanisms, which automatically drag our

attention here, there and everywhere.

At a meeting in Brussels in July this year, O’Regan and Alva

Noë of the University of California, Santa Cruz, updated the

controversial theory. Sensation, whether it be visual, auditory

or tactile, is not something that takes place in the brain, they

argue. Rather it exists in the knowledge that if you were to

perform a certain action, it would produce a certain change in

sensory input. “Sensation is not something that we feel, but

sensation is something that we do,” says O’Regan.

According to this idea, the sensation of “redness” arises from

knowing that moving your eyes onto a red patch will produce a

certain change in the pattern of stimulation in line with laws of

redness. In other words, the role of the brain is to initiate the

exploratory action and to hold the knowledge of those laws:

together this give rise to the sensation of redness.

New Scientist