Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Monday, August 14, 2017

Giving weight to illusion

The idea that our sensory processing apparatus and our brains are unreliable has been something I've come back to again and again here at Skeptophilia.  "I saw it with my own eyes" is simply not enough evidence by which to make any kind of sound scientific judgment.

Not only are we likely to get things wrong just because the equipment is faulty, our prior ideas can predispose us to get things wrong in a particular way.  Think of it as a sort of built-in confirmation bias; our brains are set up in such a fashion that when we've already decided what's going to happen, it's much more likely that's what we'll perceive.

This latter problem was demonstrated in an elegant, if disturbing, fashion in a paper released last week in Science called "Pavlovian Conditioning–Induced Hallucinations Result From Overweighting of Perceptual Priors," by Albert R. Powers, Christoph Mathys, and Philip R. Corlett, of the Yale School of Medicine, the International School for Advanced Studies (Trieste, Italy), and the University of Zurich, respectively.  Their research springboarded from previous studies wherein individuals who had been trained to associate a tone with an image were more likely to continue "hearing" the tone when shown the image with no accompanying tone than were members of a control group.

[image courtesy of the Wikimedia Commons]

What Corlett's team did was to divide participants into four groups: normal, healthy individuals; self-described psychics; individuals with psychosis who did not report hearing voices; and individuals with schizophrenia who reported hearing voices.  The researchers trained all test subjects to associate a checkerboard image with a one second long, one kilohertz tone.  They not only recorded data on which participants continued to "hear" an illusory tone when shown the checkerboard in silence, they also used a protocol (how hard they pushed the button when they heard the tone, whether real or imagined) to gauge their confidence in what they were experiencing, and they looked at neuronal activity in the brain using an fMRI machine.

The results were intriguing, to say the least.  Both the schizophrenics and the self-described psychics were five times as likely to report hearing a tone when none existed than either the control group of healthy individuals or the psychotic individuals who did not hear voices.  Not only that, the schizophrenics and the psychics were 28% more confident in their perceptions when they did hear a tone that wasn't there than were the other two groups when they made a similar mistake.

Further, the schizophrenics and psychics showed abnormal neuronal activity in two regions of the brain; the parts of the cerebrum involved in creating our internal representation of reality showed strikingly different firing patterns, and the cerebellum -- the part of the brain involved in planning and coordinating our motor responses to stimuli -- showed much lower than normal neuronal activity.

"The findings confirm that, when it comes to how we perceive the world, our ideas and beliefs can easily overpower our senses," said Albert Powers, one of the paper's authors.  Which is about as succinct a cautionary statement about trusting our judgments as I can imagine.

While the researchers specifically tested the likelihood of experiencing auditory hallucinations, I find myself wondering if this study might not have wider applications.  How do our prior perceptions bias us in general?  I know I have frequently been baffled, especially in these fractious times, how two people can see the same event and come to strikingly opposite conclusions about it.  At times, I have found myself asking, "Are we even talking about the same thing, here?"  But if our preconceived notions about the world can bias us strongly enough to hear sounds that aren't there, why should any other perception be immune to the same effect?

This possibility drives me to a disturbing conclusion.  How do you convince people that what they're perceiving is not real, if that conclusion is contrary to what their senses and their brains are telling them?

I think the key, here, is always to keep focused on the statement, "... but I might be wrong."  A lot of our faulty judgments are caused not only by our coming to the wrong conclusion, but our stubborn certainty that we are, in fact, right.  A willingness to revise our beliefs -- failing that, at least to consider the possibility that our beliefs are incorrect -- is absolutely critical.

Otherwise, we're at the mercy of sensory apparatus that are easily fooled, and a brain that bases what it perceives as much on what it already thought to be true as on the actual data it's presented with.

Which seems to me to be awfully shaky ground.

1 comment:

  1. Gordon, You've done it again. Excellent post. We evidently edit/rewrite the details of our memories each time we call them up, too. I've been mulling over an Alexandria Quartet series that hinges on just these revelations.