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Suggestion and Perception


A long time ago, at a lake cabin in New Hampshire, a friend of my parents (call him John) was talking to his daughter's boyfriend about beer. The boyfriend couldn't understand why John would drink Carling beer when Schaefer was obviously superior. John poured beer into two glasses while the boyfriend wasn't looking and asked him if he could tell which one was which. The boyfriend tried them both and clearly expressed his preference for the one he assumed was Schaefer. It turns out both were the same beer (I don't recall which one). Something peculiar was happening here. It seems that the boyfriend's perception of taste was influenced not just by taste, but by his expectation that the two beers were different.

A few years ago we had some friends at our house to try tasting different foods and drinks. One of them was vanilla ice cream. We had three brands: Haagen-Dazs, Kemps (a moderately priced brand popular in Minnesota) and an inexpensive store brand. Our guests weren't told which was which. Most of them clearly preferred both the Kemps and the store brand to the Haagen-Dazs. They were surprised since they had initially assumed that the Haagen-Dazs was better since it is quite expensive, has a high cream content, and has a top-notch reputation. Since most people try many brands of ice cream over their lives, we are likely to assume that the reputation of a "premium" ice cream like Haagen-Dazs is the result of it actually tasting better. In fact it may be that there is an illusion of tasting better caused by expectations. It turns out that in blind tests, where expectations cannot influence the perceptions, the results are often unexpected.

When we form a judgment about something we have experienced ourselves, like how much we like a beer or ice cream, we naturally assume our judgment is based entirely on our own perception. However if we have a prior expectation based on what someone has told us or something we have assumed, that expectation may have a strong influence on our opinion that we don't recognize. This is sometimes called the "power of suggestion". It can lead us to false beliefs because we think we have determined something for ourselves when in fact we are just passing on a (possibly erroneous) impression we got elsewhere. 

A common situation where perception is distorted by expectations is when people judge value on the basis of price. A friend told me a story of a shopkeeper who had some knick-knacks that had been priced at two dollars. Nobody bought them. On a whim he raised the price to five dollars. To his surprise they sold out quickly. Apparently buyers assumed that the higher price implied better quality. While it is certainly true that higher priced items have the potential to have higher quality, it is also possible that high prices are due to advertising costs, ingredients that are costlier but no better, or simply increased mark-up.

A number of years ago the concept of "pyramid power" became popular. It involved the belief that pyramid shaped structures somehow focused power in a way that was beneficial to things inside them. One of the claims was that razor blades would stay sharper if stored in a pyramid shaped container between uses. People who tried this were quite confident that it worked, but their judgment was made with full knowledge of whether the blades they were using had been stored in the pyramid. When testing was done without the possibility of bias, the effect disappeared. While it is relatively harmless if we make mistaken judgments about the taste of ice cream or beer, the pyramid case can be troublesome because it could lead people to mistakenly believe in a miraculous effect that would invalidate important principles of science. If taken seriously, scientists could waste a lot of time and money trying to develop a scientific theory about an effect that did not exist.

This type of problem is well known in science as the "placebo" effect, and it often makes doing scientific experiments considerably more difficult. Imagine that a new pain killing drug is being tested. If the patients who are given the drug are expecting it to benefit them, they are likely to report a benefit even if the drug is ineffective. It may be that they actually feel better just because they know they are getting some sort of treatment, or it may be that, believing the drug to be effective, they assume they would have felt worse without it. To prevent getting erroneous results because of this effect, experiments are usually designed so that patients do not know whether they are getting a real treatment or a fake treatment (known as a placebo). If the fake treatment is just as helpful as the real one, then it is likely that any benefit reported from the real one is just caused by the placebo effect and not the drug.

A dramatic case of suggestion influencing perception occurs with a phenomenon known as "facilitated communication" which involves children with autism. Martin Gardner (2001)provided the following description of how it works (Gardner uses masculine pronouns for the child since most autistic children are male):

An autistic child is seated at a typewriter or computer keyboard, or perhaps just a sheet of paper with the keyboard drawn on it… A therapist, usually a woman, is called the child's "facilitator." She asks the child a question, then grasps his wrist, or elbow - usually the hand - while the child extends his index finger and begins to type. The belief is that the child has the ability to communicate intelligent thoughts by typing, but lacks the muscular coordination needed for finding the right keys. The facilitator assists him in locating the keys she is sure he intends to hit.

A wondrous miracle now seems to take place. Although the child has been thought to be mentally retarded, unable to read, write, or speak coherently, he types out lucid, sophisticated messages that could only come from a normal intelligent mind.


The children were apparently able to answer questions, identify pictures, and tell about their feelings. Facilitated communication was adopted in many treatment centers around the world and described in newspapers and magazines including Readers Digest. Some people, however, recognized serious problems with the method, such as the fact that the child often was not looking at the keyboard when he chose the keys. Eventually some tests were done where the child was asked a question using earphones so the facilitator could not hear what was said, and sure enough, the answers were unrelated to the questions. In another test the child was shown a picture and the facilitator was shown a different picture but led to believe it was the same one the child saw. The typing represented what the facilitator saw rather than what the child saw. Clearly facilitated communication did not really work to communicate the child's thoughts, but instead communicated the facilitator's expectations.

How does this related to things like beer tasting and placebos? It is widely agreed that the facilitators were sincere people who were not deliberately faking the results. Their choice of keys was based on their own expectations of what the child might want to say rather than their actual perception of the child's movements. So, like people tasting foods or taking placebos, their perceptions were misled by their expectations.

The problem presented by facilitated communication was particularly serious because some of the messages wrongly believed to have come from the autistic children involved accusations of sexual abuse. Dozens of men were arrested based on this fallacious "testimony", and some spent jail time before it was recognized that the information was totally invalid.

An interesting case of mistaken perception was described by Phil Klass, an investigator of UFO claims:
At approximately 8:45 P.M. CST on the night of March 3, 1968, three well educated adults, standing outside near Nashville, Tennessee, saw what they later described as a giant, saucer-shaped, metallic craft with many square-shaped windows illuminated from inside the craft, headed out of the sourthwest toward the northeast. It passed overhead silently at an altitude estimated at only one thousand feet.

The U.S. Air Force also received a UFO sighting report from six persons living near Shoals, Indiana, some two hundred miles north of Nashville, who said they had seen the same object, which was described as being cigar shaped, with numerous square windows illuminated from inside, and with a rocketlike exhaust emitted from the rear of the craft. (Klass, 1981)

It turns out this object was the reentry of a Russian rocket booster that had been used to launch the Soviet Zond 4 spacecraft. Why did people describe it as having an oblong or saucer shape, the windows as square, and only a thousand feet up when it was actually high in the sky hundreds of miles away? Probably because human perception tries to match what is seen with known objects. In this case, an airliner seen in the dark with lit windows would have looked similar to the row of bright rocket fragments, so they probably used this as a starting point for their judgments about the object. An airliner would be expected to have square windows, and judgment of its distance would be based on the spacing of the "windows" from each other. Their minds would have filled in the details, and since the whole sighting took place in the span of just a few seconds, there was no opportunity for more thoughtful examination. The end result is that reliable people, attempting to be perfectly honest, tell a false story. This is a quite normal type of human error, and could happen to any of us.

Normally when we are confident someone is honest and they tell us that they have learned something through direct personal experience, we feel it must be true. This applies even more so when we feel we ourselves have learned something from our own experience. Hopefully the above examples show that even though people are honest, sane, and perfectly intelligent, they can still have experiences and perceptions that are wrong. It is important to take this into account when we are trying to determine what is true.