4.7: Perceptual Set- The Role of Expectations

What is the character in the middle of Figure 4.7.1? If we block out the 12 on the left and the 14 on the right, we just see the column, and we naturally, almost automatically, see the middle character as a B. But block out the A and the C, and it instead looks like a 13.

Figure \(\PageIndex{1}\): What’s that in the Middle?

Here the context influences our expectations, so that we tend to see what the context leads us to expect we would see. To test this claim, we could show one group of people the three characters on the row and another group the three characters in the column. When we do this, we find that context does indeed influence how people see things. This example also shows how cultural issues, our having the language and alphanumeric characters that we do, affect how we see things.

People from a much different culture might not see this figure as anything but a series of meaningless marks. In fact, there is evidence that the perception of certain visual illusions vary from one culture to another.

Can you think of a context that might lead people to see some of the ambiguous figures in one way rather than another? Figure 4.7.2 should give us a clue. Here we plop our ambiguous creature down into two different contexts.

Figure \(\PageIndex{2}\): Two Group Portraits

Now answer the following questions:

1. If you first saw the group portrait of the ducks, how do you think you would have interpreted the picture of the lone creature?
2. What if you had instead seen the group portrait of rabbits?
3. Do you think it would have made any difference if someone had first said to you “I’m going to show you a drawing of a duck?”
4. How do you think that people who had seen lots of rabbits but no ducks would see it?

These are empirical questions, and the only way to answer them is to check and see what people in fact do under such conditions. But we know the effect these examples have on us, so we have something to go on. In a moment, we will consider some further cases that will provide more evidence about the correct answers.

What you expect to see can strongly influence what you do see. Psychologists say that your beliefs and expectations (and, as we will see in a bit, your desires) constitute your perceptual set.

The context helps determine your perceptual set, because it influences what you expect to see. In some contexts, you expect to see one sort of thing, say a duck. In other contexts, you may expect to see something else, say a rabbit. In normal situations, you would be upset if coins simply began to vanish into thin air. But when you watch a magician, you expect coins that seem to disappear.

It Just Isn’t in the Cards: Classification and Set

Context is one important determinant of perceptual set, but it isn’t the only one. An experiment done in 1949 supplies some surprising insights into the way that our expectations are influenced by our ways of classifying things. Jerome Bruner and Leo Postman presented subjects with a series of fivecard hands of playing cards that flashed briefly before them for periods of a second or less (nowadays, this would be done on a computer screen). The hands contained many normal cards, but some cards were anomalous. On these cards, the hearts were black and the spades were red.

It took people longer to recognize these trick cards than to recognize normal cards. At one or more points in the experiment, almost all the subjects reported an anomalous card as being normal. For example, they assimilated the black three of hearts to a normal three of hearts (here the shape dominated) or to a normal three of spades (here the color dominated).

The subjects had a system of classification: cards come in four suits (hearts, diamonds, spades, and clubs) with cards in the first two suits being red and cards in the last two suits being black. This led them to expect certain things, and in some cases, these expectations led them to misperceive a trick card.

The influence of our expectations and beliefs and desires on perception involves top-down processing. Both bottom-up and top-down processing are important. There is still some controversy about the relative importance of each (and of additional sorts of processing we won’t go into here); it might be thought, for example, that top-down processing only plays a substantial role in cases where the object of perception is ambiguous. But even if some scientists overestimate the significance of top-down processing, the following examples show that beliefs and expectations, desires and emotions, can have a substantial impact on how we see and interpret normal objects outside of the laboratory.

Real-life Examples

There is sometimes disagreement about how to interpret laboratory studies, and even when there isn’t, they can seem a bit artificial. But there can be little doubt that our perceptual sets influence the ways that we see things in the world outside the laboratory—sometimes with disastrous results.

It Looked Like a Bear

Elizabeth Loftus and Katherine Ketcham report a case of two men who were bear hunting in a rural area of Montana. After an exhausting day in the woods, night was falling, and they were making the trek home. On the way, they talked about bears. Suddenly, as they rounded a bend, a large, moving object loomed up ahead of them. Both men took it for a bear, raised their rifles, and fired.

It turned out to be a large, yellow tent with its flap blowing in the wind. A couple was inside, and the woman was killed. The hunter who shot her was tried (and convicted) of negligent homicide. The jury found it incomprehensible that he could have mistaken a yellow tent for a bear. But he was primed to see a bear; he had bears on the brain. His perceptual set played a powerful role in leading him to see things in the way that he did. Most of us have probably made similar mistakes, though hopefully with less tragic results.

Schizophrenic or Normal?

In 1973, researchers had a mentally healthy adult check himself into a mental health facility with complaints of hearing voices. He was classified as having schizophrenia and admitted. Once in the hospital he never said anything about the voices, and he behaved like his usual self. But the members of the hospital staff had been led to expect person with schizophrenia, and that is how they continued to see him.

They recorded his “unusual” behavior (he spent a lot of time writing down his observations), often talked to each other as though he wasn’t present (this is common behavior in psychiatric facilities) and didn’t realize that he was behaving normally. Once they had a label, they didn’t check to see how well it fit. It took, on average, almost twenty days for the subject to get himself released. This is not a case where people misperceived something they only glimpsed for an instant. Here the staff was around the subject for almost three weeks. Interestingly, some of the hospital patients were much quicker to see that the subject’s behavior for what it was (what might explain this?).

Everyday Errors

Misperception is far from rare. Here are three examples; can you think of some more?

• Most of us have seen a person in the distance and thought they were someone we know. When they got closer, we realized that they don’t look anything like the person we expected.
• Proof-reading provides similar examples. As you read back over teh first draft you expect to see words spelled in a certain way, and things often look as you think they should. It is very easy to read right past the ‘teh’ there on the page—though once you do notice it, it jumps off the page at you.
• If you don’t normally live alone and find yourself home all by yourself (especially if you have just seen a scary movie), shadows in the backyard and sounds in the attic can take on new and sinister forms.