Last week I blogged about lying: “Everyone Lies: Why?”

Deception is one thing, self deception is quite another. This week TED.com has posted my new TED talk, delivered at the last TED conference, in which I present material from my forthcoming book on the neuroscience of belief, tentatively entitled The Believing Brain, a central theme of which is how we are so easily deceived and how we deceive ourselves. Here is a brief summary of the thesis of the talk, although because it is so visual I strongly recommend watching the TED video.

Souls, spirits, ghosts, gods, demons, angels, aliens, intelligent designers, government conspiracists, and all manner of invisible agents with power and intention are believed to haunt our world and control our lives. Why?

The answer has two parts, starting with the concept of patternicity, which I define as the human tendency to find meaningful patterns in meaningless noise. The face on Mars, the Virgin Mary on a grilled-cheese sandwich, Satanic messages in rock music. Of course, some patterns are real: finding predictive patterns in changing weather, fruiting trees, migrating prey animals and hungry predators was central to the survival of Paleolithic hominids.

The problem is that we did not evolve a baloney-detection device in our brains to discriminate between true and false patterns. So we make two types of errors: a Type I error, or false positive, is believing a pattern is real when it is not; a Type II error, or false negative, is not believing a pattern is real when it is. If you believe that the rustle in the grass is a dangerous predator when it is just the wind (a Type I error), you are more likely to survive than if you believe that the rustle in the grass is just the wind when it is a dangerous predator (a Type II error). Since the cost of making a Type I error is less than the cost of making a Type II error, and since there’s no time for careful deliberation between patternicities in the split-second world predator-prey interactions, natural selection would have favored those animals most likely to assume that all patterns are real.

But we do something other animals do not do. As large-brained hominids with a developed cortex and a “theory of mind”—the capacity to be aware of such mental states as desires and intentions in both ourselves and others—we practice what I call agenticity: the tendency to believe that the world is controlled by invisible intentional agents. That is, we often infuse the patterns we find with agency, and believe that these intentional agents control the world, sometimes invisibly from the top down (as opposed to bottom-up causal randomness). Together, patternicity and agenticity form the cognitive basis of shamanism, paganism, animism, polytheism, monotheism, and all modes of Old and New Age spiritualisms.

Agenticity carries us far beyond the spirit world. The Intelligent Designer is said to be an invisible agent who created life from the top down. Aliens are often portrayed as powerful beings coming down from on high to warn us of our impending self-destruction. Conspiracy theories predictably include hidden agents at work behind the scenes, puppet-masters pulling political and economic strings as we dance to the tune of the Bildebergers, the Rothchilds, the Rockefellers or the Illuminati.

There is now substantial evidence from cognitive neuroscience that humans readily find patterns and impart agency to them, well documented in the University of Bristol psychologist Bruce Hood’s new book SuperSense (HarperOne, 2009). Examples: Children believe that the sun can think and follows them around and they often add smiley faces on sketched suns. Adults typically refuse to wear a mass murderer’s sweater, believing that “evil” is a supernatural force that imparts its negative agency to the wearer (and, alternatively, that donning Mr. Rogers’ cardigan will make you a better person). A third of transplant patients believe that the donor’s personality is transplanted with the organ. Genital-shaped foods (bananas, oysters) are often believed to enhance sexual potency. Subjects watching geometric shapes with eyespots interacting on a computer screen infer that they represent agents with moral intentions.

“Many highly educated and intelligent individuals experience a powerful sense that there are patterns, forces, energies, and entities operating in the world,” Hood explains. “More importantly, such experiences are not substantiated by a body of reliable evidence, which is why they are supernatural and unscientific. The inclination or sense that they may be real is our supersense.”

We are natural-born supernaturalists.