Since the earliest phase of the Enlightenment, much of Western scholarship has been haunted by the idea that consciousness is not entirely attuned to the cumulative content of the mind. In his Ethics, the Dutch thinker Baruch Spinoza submitted that man can never be aware of everything he is, as that would entail a personal experience of bodily functions, internal chemistry, and even God. Later on, the Austrian neurologist Sigmund Freud proposed a general theory of the unconscious – that menacing undertow of the human experience, whereby suppressed urges and instincts influence our conscious life.

Now, this strange and often unsettling field of inquiry has begun to engross neuroscientists and psychologists as well. In a recent study, researchers at the University of Arizona describe how the brain can process and synthesize visual information without producing a concomitant conscious understanding. In other words, it would appear that we can see things without really seeing them.

Sense & Nonsense

Published in the journal Psychological Science, the study sought to evaluate the validity of one of psychology’s central assumptions – namely, that only objects access semantics. Essentially, this means that the brain will only assign meaning to visual input that conforms to its understanding of shape. Shapeless, amorphous input will be dismissed as nonsense – literally.

To test this assumption, doctoral candidate Jay Sanguinetti and his colleagues enrolled a number of volunteers in an experiment. While the researchers monitored their brain activity with electroencephalography (EEG) imaging, the subjects were asked to look at a series of black silhouettes against white backgrounds. Although all silhouettes were abstract, some contained traces of meaningful, real-world objects. For example, one image contained the partial outline of a seahorse – a patently irregular yet distinct shape. The researchers then analyzed the recorded EEG activity to determine whether the average subject’s brain assigned meaning to this subset of fragmented real-world objects.

"We were asking the question of whether the brain was processing the meaning of the objects that are on the outside of these silhouettes," Sanguinetti said in a press release. "The specific question was, 'Does the brain process those hidden shapes to the level of meaning, even when the subject doesn't consciously see them?’"

Intriguingly, the answer appears to be yes. EEG imaging revealed that while none of the participants consciously understood the partial objects, their brains nonetheless assigned meaning to them. "The participants in our experiments don't see those shapes on the outside; nonetheless, the brain signature tells us that they have processed the meaning of those shapes," senior author Mary Peterson told reporters. "But the brain rejects them as interpretations, and if it rejects the shapes from conscious perception, then you won't have any awareness of them."

Demon in the Rough

The current study recalls a number of equally mind-boggling papers published earlier this year. In “Language Can Boost Otherwise Unseen Objects into Visual Awareness,” researchers from Yale University demonstrate that words and language cues can make us see things that aren’t there. In another study, neuroscientists at Vanderbilt University show that the brain continues to perceive the body in complete darkness.

For those shivering at the prospect of not really knowing everything they know, it may be beneficial to return to philosophy. In Meditations on First Philosophy, the French thinker Rene Descartes provides some existential relief with his evil demon hypothesis. The thought experiment suggests that even if everyone and everything around you is the illusory result of a long con perpetrated by an evil demon, you will still be you, as your conscious experience of the world will still hold true. In other words, no matter how inadequate your awareness is, no one can say that you’re living a lie.

And in the end, isn't that all that matters?

Source: Joseph L. Sanguinetti, John J. B. Allen, and Mary A. Peterson. The Ground Side of an Object: Perceived as Shapeless yet Processed for Semantics. Psychological Science 0956797613502814, first published on November 12, 2013.