The Believing Brain - Michael Shermer [65]
Increasing dopamine increases pattern detection; scientists have found that dopamine agonists not only enhance learning but in higher doses can also trigger symptoms of psychosis, such as hallucinations, which may be related to that fine line between creativity (discriminate patternicity) and madness (indiscriminate patternicity). The dose is the key. Too much of it and you are likely to be making lots of Type I errors—false positives—in which you find connections that are not really there. Too little and you make Type II errors—false negatives—in which you miss connections that are real. The signal-to-noise ratio is everything.
Patternicity in the Brain
In his Pulitzer Prize–winning book The Dragons of Eden, Carl Sagan conjectured where in the brain superstition and magical thinking are likely to be found: “There is no doubt that right-hemisphere intuitive thinking may perceive patterns and connections too difficult for the left hemisphere; but it may also detect patterns where none exist. Skeptical and critical thinking is not a hallmark of the right hemisphere.”13 In an extension of the experiment by Susan Blackmore discussed in chapter 4, in which she found a difference between believers and skeptics on the propensity to find meaningful patterns in meaningless noise, Peter Brugger presented random dot patterns in a divided visual field paradigm so that either the left hemisphere (via the right visual field) or the right hemisphere (via the left visual field) of the brain was exposed to the image. (Recall that our brains are split down the middle and divided into two hemispheres connected in the middle at the corpus callosum; inputs from the left side of the body go to the right hemisphere and inputs from the right side of the body to the left hemisphere.) Brugger found that his subjects perceived significantly more meaningful patterns in the right hemisphere than in the left hemisphere, and this happened for both believers and skeptics.14
Subsequent studies found hemispheric differences between believers and skeptics. In one study, Brugger’s team had blindfolded subjects hold a rod in their hands and physically estimate its middle point. Subjects were also given the Magical Ideation Scale questionnaire, which measures paranormal beliefs and experiences. What the scientists found is bizarre: believers in the paranormal estimated the middle point of the rod more to the left of center, which means that their right hemispheres were influencing their perception of space and distance. Brugger’s lab then ran another experiment in which strings of letters forming either a word or nonsense were presented to the left visual field and the right visual field, instructing the subjects to respond when they recognized a word. The subjects also rated their belief in ESP on a six-point scale. Results: skeptics had greater left hemispheric dominance compared to believers, and believers had superior right hemispheric performances compared to skeptics. Adding EEG measures to the experiment revealed that believers had more right hemisphere activity compared to disbelievers in ESP.15
What does all this mean? Split-brain studies show that there are many distinct differences between the left brain and the right brain, but that the differences are far more subtle and nuanced than originally believed (thereby discounting most of the claims made in the endless stream of self-help books published on how to, for example, improve your right brain by using your left hand more, or improve your left brain through certain right-handed exercises). Nevertheless, there are dissimilar tendencies between the hemispheres, with the left cortex dominant in verbal tasks such as writing and speaking, and the right cortex dominant in nonverbal and spatial tasks. It’s too simple to say that the left hemisphere is your literal, logical, rational brain and your right hemisphere is your metaphorical,