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While seated at a table, you are shown a picture of a chicken claw. On the table, a number of pictures are spread out in front of you. You are pointing at a picture of a shovel. Why?

The answer to that question helps explain why, when Malaysia Airlines Flight MH370 vanished, and there were few known facts, so many people were so confident that they knew what had happened – and so many more listened to them.

Students of neuroscience will recognize the chicken-claw scenario. It comes from the seminal research of Michael Gazzaniga, the University of California psychologist renowned for his work with "split-brain" patients – people who have no connection between the left and right hemispheres of the brain, usually because the connection has been severed surgically as a treatment for severe epilepsy. Split-brain patients function remarkably well. But Prof. Gazzaniga and future Nobel laureate Roger Sperry realized that the lack of connection between the hemispheres, in combination with certain peculiarities of the brain's sensory wiring, made it possible to communicate with one hemisphere while leaving the other entirely in the dark. It was as if the two hemispheres were two separate people. And that opened new ways to explore how the brain functions.

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In the example above, Prof. Gazzaniga showed the right hemisphere – and only the right hemisphere – an image of a snow storm, then asked it to point to the picture on the table that was connected to that image. Naturally, it pointed at the shovel. Then the left hemisphere was shown a picture of a chicken claw, followed by the big question: Why are you pointing at a shovel?

The left hemisphere did not know why. But that wasn't its response. "Oh, that's simple," one patient told Prof. Gazzaniga. "The chicken claw goes with the chicken and you need a shovel to clean out the chicken shed."

The left hemisphere is the location of what Prof. Gazzaniga dubbed "the interpreter," the portion of the brain whose job is to make sense of new information by generating a plausible explanation. The interpreter is relentless. And ingenious. Even confronted with bizarre facts that seemingly defy explanation, it can usually draw on existing perceptions and beliefs – such as, "chicken coops have to be cleaned out with a shovel" – to dream up an explanation. If there are few or no facts, that's no problem. That may even make the job easier, because there is less information the interpreter's explanation has to account for and it can simply use existing perceptions and beliefs to fill in the blanks: Jet disappeared? Terrorists. Who are terrorists? Muslims. So Islamic fanatics did it. It's obvious.

This automatic and effortless generation of hypotheses is not a bad thing. In fact, it's an essential skill, or it wouldn't be wired into every human brain. But it can get us into trouble when we don't think carefully and cautiously, and instead leap from confusion and uncertainty ("I have no idea why my hand is pointed at a picture of a shovel") to a clear and confident conclusion ("Oh, that's simple") without spending any time in between ("This is one possible explanation but there may be others").

Unfortunately, it's normal to make that leap. An explanation that neatly wraps up observed facts gives us a feeling of confidence. It feels true. We equate that feeling of knowing with knowing. We are convinced. We know. We then process new information accordingly, accepting without question whatever supports the belief while being hyper-skeptical and dismissive of whatever does not. Almost inevitably, the strength of our conviction grows.

Investigators, such as those who try to figure out what's happened to missing planes, are specifically trained to avoid "tunnel vision." Don't focus on the first hypothesis that comes to mind. Search for other explanations. Recognize that all hypotheses are only tentative guesses based on what's currently known. Scoop up as much information as possible, leaving a slow and careful evaluation of the quality and meaning of the evidence for later.

Of course, doing this requires the investigator to say, the whole time, "I don't know. Like everyone else, I have hunches and feelings, but I will not confuse these with knowing. I do not know."

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That is a challenge. Suspending judgment means acknowledging uncertainty. For the sense-making machinery in the brain, that is frustrating, almost painful, although how unpleasant it is varies from person to person. Psychologists measure that discomfort with a "need for closure" scale. Score low on "need for closure" and you may make an excellent aircraft accident investigator.

Score high and you are, in the words of Arie Kruglanski, the psychologist who helped developed the scale, the sort of person who responds to uncertainty by insisting on an answer – "any answer." For these people, conspiracy theorists and 24-hour news channels await.

Judging by CNN's soaring ratings, there are an awful lot of them.

Dan Gardner is the Ottawa-based author of Risk: The Science and Politics of Fear and Future Babble: Why Expert Predictions Fail – and Why We Believe Them Anyway.

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