As I wrote last time, much of what I’m reading lately focuses on how the human brain manages to generate the human experience.

And much of that reading centres on a single feature of cognition: most of what we think is unconscious, and much of it is involuntary.

Traditional rationalism sees these inner processes as essentially chaotic, as the source of the puzzling inaccuracy of our thinking, especially of the logical lapses which characterize our reasoning. Where do these weaknesses come from, and why do we have them?

“Quantum Minds,” by Mark Buchanan, the cover article in the September 3rd issue of *New Scientist, *claims that “the fuzziness and weird logic of the way particles behave applies surprisingly well to how humans think.”

No one is arguing that the brain is a quantum organ. But the mathematics used to describe the world of quantum physics seems also to describe the workings of our brains.

As Diederik Aerts of the Free University of Brussels, Belgium, puts it: “People often follow a different way of thinking than the one dictated by classical logic. The mathematics of quantum theory turns out to describe this quite well.”

Many experiments have traced how poorly we do on some kinds of probability tests. Classical logic should steer us clear of these errors, but it doesn’t. But quantum mathematics offers an alternative view.

The iconic “double slit” test shows how quantum probabilities differ from their classical cousins. In our everyday experience, probabilities add up. If you flip a coin once, the probability of heads is 50%. If you flip it again, the probability of at least one heads goes up to 75%. (Three of the four possible combinations of heads and tails on two flips include at least one heads.)

Quantum probability doesn’t work that way. The double slit photon test produces a characteristic “stripe” pattern, revealing that there is an “interference” factor at work. In quantum events, probability consists not just of adding up the individual chances of each event, but also of adding in an interference effect, which can be either plus or minus.

What you get is a “fuzzy probability,” a range rather than a value. Something to do with Hilbert Space. Don’t ask me to explain it any better than that. If I could have, I would have. Just trust them — they’re scientists, so they know everything.

This kind of interference pervades quantum physics, and the mathematics used to describe it can be applied to the “fuzzy” way we think. It seems that our brains, which aren’t quantum environments, nevertheless experience a similar kind of interference effect.

When experimenters offered subjects a chance to play a game in which there was an equal chance of winning $200 or losing $100, clear majorities of subjects who knew the result of their first game chose to play a second time. Why not, since the straight odds indicate that playing twice wins money three times out of four. But when subjects weren’t told whether or not they had won, they chose to play again less than 40% of the time. Why should this be? The odds didn’t suddenly change.

What appears to be happening is that the presence of two situations — I won the first game, or I lost the first game — yields odd results. It’s the cognitive equivalent to two slits. In another experiment, subjects had no trouble placing X in the Y category when told that “all X are Y.” But some people couldn’t put X into the disjunctive category “Y or Z.” Again, the presence of two situations produces a perception of “interference.”

And it’s not just quantum probability that gives insight into the ways our brains work. Perhaps the best known tenet of quantum physics is the “uncertainty principle,” in which some of the characteristics of an object are not determined — do not exist — until they have been contextualized by being measured.

In quantum physics, contextuality is the way that particular kinds of measurement change the properties of the particles they measure. The equivalent in cognition, Aerts argues, is the contextualization of words. As Buchanan puts it, “A tall chihuahua is not a tall dog.” And a “red barn” is not the same “red” as are “red eyes.” Aerts writes, “The structure of human conceptual knowledge is quantum-like because context plays a fundamental role.”

The insight that we conceptualize in a quantum-like way, and that our language reflects this way of thinking, is pointing other scientists toward new ways of organizing computer intelligence. Google researcher Dominic Widdows are building quantum mathematics into new search engines. In a typical web search, for instance, a geologist who searches “rock” will get millions of irrelevant hits relating to rock music. Add the negating boolean term “-songs,” and you’ll still get tons of rock music pages that merely don’t use the word “song.” If all of the words associated with song are grouped together contextually, then “not” becomes a much more effective limiter.

So haven’t we drifted rather far from where we started? Yes, and no. The application of quantum mathematics to human cognition and its replicator, AI, reinforces the idea that most of our “thinking” is not classically rational. If our brains in fact do work with “fuzzy logic” and quantum-like contextual word-fields, that would explain a lot of the otherwise inexplicable mental processes that underlie our conscious minds.

On the unconscious level, it would seem, our minds do not follow the strict formal rules of classical logic any more than quantum states in physics follow the strict formal descriptions of classical physics. Newton, meet Heisenberg. Conscious mind, meet unconscious brain.

Unlike those who resist the physical description of the ways the mind works, I find explanations like this compellingly fascinating. Rather than making up fairy stories or relying on speculative dualities, thanks to cognitive science we are coming ever closer to “seeing” into the complexities of our own minds.

Living in a physical world, as we do, that’s certainly the most fantastic voyage we can ever take.