In one sense, the main theme of the Being Human conference was "illusion." Illusions occur when what we perceive does not match with the true state of the world. When our thoughts do not accurately reflect objective reality. Visual illusions make this obvious, and we usually enjoy them. We see one white square and one black square, but they turn out to truly be the same shade of grey. Or two lines of equal length appear to be different. A waterfall flows ever downward yet somehow also falls up.

Magicians stake their careers on the idea that humans enjoy being fooled. Perhaps we enjoy illusions when we are prepared to experience them. But other illusions are so powerful, so pervasive, so woven into the fabric of human experience, that pointing them out makes us supremely uncomfortable. Perhaps it is that discomfort that prompts us to try to pick apart the mysteries of human experience. Scientists and artists alike attempt to peer under the hood of Homo sapiens, hoping to catch even a fleeting glimpse of the inner machinations of mind and brain. We build monuments to their complexity: giant helium-cooled magnets called MRI machines, or tangles of wires knitted into an EEG hat. You think free will is a complicated question? Try the perception of color.

Scientist-artist Beau Lotto pointed out that even something as simple as the perceptual experience of color is subject to illusion; the colors we perceive are not necessarily indicative of the physical nature of the light that hits our retinas. Our brain is, in other words, prepared to interpret certain parts of the visual field differently, depending on the surrounding context. The white and grey squares on either side of the table leg (below) are actually the same color. But the presence of a shadow causes your brain to experience them differently.

In a fun demonstration with Peter Baumann, Lotto also pointed out that our perception of where our bodies are in space is also an illusion of sorts. Baumann was asked to practice hitting a target some 10 feet away with a small ball. Then, he put on prism glasses, which shifted his visual field by 20 degrees. The result was that it appeared to Baumann as if the target was several feet to the right. With some trial and error, however, he quickly learned to overcompensate for the shift, by throwing to the left. This is something that water birds do without effort as they dive for fish, which are actually inches away from where they seem to appear. And, as was expected, when he removed the glasses, he persisted in throwing the ball too far to the left! It's not vision that is changing, per se. Instead, what changed was Baumann's perception of the location of his body in space. Just as with the visual illusions above, the prism glasses created a sort of proprioceptive illusion. Change the environment, and you change behavior.

Illusions aren't all fun and games, though. The illusion of a phantom limb - and the therapy to alleviate its associated pain - (what else would V.S. Ramachandran have spoken about?) is just as real as the color illusions, and just as confusing, but has important therapeutic and public health implications. The existence of phantom limbs shows us that even the sensory awareness of our own bodies is, in its own way, illusory. Using just a cheap mirror, Ramachandran has been able to reduce the pain felt by hundreds of sufferers of phantom limb pain. These are people who, due to some accident or injury, have had one or more of their limbs amputated. Despite the rational knowledge that their limbs are missing, some part of the brain doesn't know this. Some neurons still fire as though they are receiving sensory information from those limbs, and when those feelings are of pain, it's bad news. How can a doctor provide therapy, though, for a limb that doesn't even exist? By tricking the visual system into perceiving the physical presence of the missing limb - with just a mirror reflecting the image of the opposite limb - Ramachandran can help these patients feel better. One illusion is used to counter the effects of the other.

But you don't need a missing limb to experience this. By covering up someone's hand with a cloth and placing a rubber hand next to it, scientists have been able to re-write a person's mental body plan. First, the experimenter simultaneously stimulates the real hand (outside the view of the participant) and the rubber hand. The participant very quickly begins to perceive the rubber hand as his own. Then, the experimenter does something surprising: he stabs the rubber hand with a fork. The participant knows that it isn't really his hand. Still, he recoils at the sight of impending danger to the false appendage. It isn't just our body's location in space that can be illusory, but even the things that constitute the body in the first place!

Illusions of vision and illusions of the body are one thing, but what can really bother people are the illusions of choice. Laurie Santos created of a token economy in a colony of capuchin monkeys at Yale. Monkeys were trained to trade metal washers for food. Despite the fact that no other species naturally uses any sort of market economy, these monkeys learned to use money to buy food quite easily. But here's the really interesting part: their decisions were subject to the same sorts of biases as humans. Their decisions, and ours, are irrational. For example, capuchins tended to favor smaller, sooner rewards over larger, future rewards under some circumstances. Just like us. Presented with two mathematically equivalent decisions, monkeys chose differently depending on how the information was presented. Just like us. Of course, we think our decisions are rational. Isn't rational thought what separates man from monkey? Call it the illusion of rational decision-making. (And: the illusion of thinking that humans are qualitatively different from non-human animals.)

This illusion doesn't end with economic decisions. Did you know that a disproportionate number of dentists are named Dennis or Denise? It's true, at least according to David Eagleman. And people are more likely than would be expected by chance to marry someone who shares the same first initial. John and Jamie. Mark and Michelle. These are quite clearly bad ways to choose careers or to choose mates, and yet those patterns exist. In real life. We only think we control our choices. It's all an illusion.

Given that so much of the human experience is built upon illusion, what does this say for what it means to be human? In his talk, Eagleman pointed out that the brain is more like a parliament than a monarchy. And the "you" that you perceive to be in the driver's seat is but one voting member of a larger assembly. The self is, in a very real way, an illusion. Most of the neural computations that comprise each of "your" behaviors and "your" experiences occur below the level of conscious awareness. Imagine, Eagleman said, that a computer gained autonomous control over each of its peripheral devices, ripped the cover off of the tower, and pointed the webcam at the circuits and wires inside. This, essentially, has described much of the human scientific endeavour. And we're the only species that does this. We are the only species that is obsessed with its own purpose and origins. We're the only species (contrary to some accounts) that gets together to discuss the nuances of what it means to be us. Perhaps this, precisely, is what it means to be human.

Still, I wonder: if everything is, in one way or another, an illusion, then what kinds of answers we can expect to find? Are we just fooling ourselves?


Videos of the talks from Being Human 2012

Science 2.0 at Being Human - by Hank Campbell

Images: visual illusions via LottoLab and also Wikimedia Commons. Header image via Flickr/Being Human 2012.