Chapter 35. Perceptual Set

Learning Objectives

bottom-up processing
analysis of the raw input from the sensory systems in order to construct a perception of the outside world
perceptual set
an expectation of what will be perceived; through top-down processing, influences what is actually perceived
perception
organizing and interpreting information from the senses to understand its meaning
top-down processing
using existing knowledge or beliefs to interpret the sensory information, leading to faster perception but also to errors
Perceptual Set
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Photo: a human figure in a bizarre position or location
Christophe Kiciak/Getty Images
Learning Objectives:

Describe the role that perceptual set plays in influencing perception.

Explain the connection between perceptual set and top-down/bottom-up perceptual processing.

Review

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Review

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Illustration: simple illustration with an ambiguous figure in the center, representing either a letter “B” or the number “13”; start with the number string “12 13 14” displayed horizontally; then add “A” and “C” so that the vertical elements appear to read “A B C”; adjust the center item until it can be interpreted as either a “B” or a “13”

1. Sometimes, we perceive what we expect to perceive rather than what is actually there. This principle is called perceptual set—a tendency or predisposition to perceive a particular object or event. For example, if you were asked to read the numbers in this image, you would perceive the middle item as the number 13. But if you were asked to read the letters, you would perceive the middle item as the letter B.

Review

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Review

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Illustration: simple illustration similar to reference image, with two arrows, one pointing up and one pointing down; upward-pointing arrow labeled “Bottom-up processing” with small-text description “Begin with raw sensory information, then assemble it and form an interpretation”; above arrow point show larger text “What could this be?”; downward-pointing arrow labeled “Top-down processing” with small-text description “Begin with prior knowledge and beliefs, then apply them to the sensory information”; below arrow point show larger text “Is this what I think it is?”

2. Perception involves an interplay between bottom-up processing and top-down processing. Top-down processing generates tentative ideas about the objects around us, and then tries to map those ideas onto the sensory input generated from bottom-up processing. Perceptual set influences top-down processing by providing expectations about what we will perceive.

Review

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Review

Select the NEXT button to continue with the Review.

Illustration: try to get permission to use this standard “impossible figure” by Roger Shepard, based on an elephant; if not, produce an illustration similar to the other reference images of a hand; the hand should show four fingers leaving the hand, but the fingertips are shifted into the empty space between the fingers

3. If the sensory input from bottom-up processing matches the expectations from top-down processing, we move on to produce a final interpretation of what is happening around us. But in cases where the input clearly doesn’t match our expectations, we need to generate new ideas and try again to match those ideas with the sensory evidence. If you expect to see an elephant, at first glance, this elephant looks normal. It’s only when you start counting the elephant’s legs that you realize your initial interpretation of the sensory information needs to be revised.

Practice 1: Creating an Expectation about Age

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Practice 1: Creating an Expectation about Age

Select each of the buttons to see what would probably happen if you viewed the drawings in the sequence indicated.

When you look at a picture, your perceptual system is simultaneously using bottom-up processing (analyzing the raw sensations from the eyes to construct an interpretation of the picture) and top-down processing (using your expectations about the picture to guide the analysis of the raw sensations). Perceptual set is a mental predisposition that influences top-down processing by imposing a specific concept or idea about what you will see.

Illustration: image is clearly a young woman (on left), labeled “A - Young woman”
What happens if you view Drawing A before Drawing C?
Illustration: image is clearly an old woman (on right), labeled “B - Older woman”
What happens if you view Drawing B before Drawing C?
Illustration: image C is the ambiguous figure (middle), labeled “C - Ambiguous”

Practice 2: Creating an Expectation about Gender

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Practice 2: Creating an Expectation about Gender

Select the NEXT IMAGE button to move through this perceptual set example.

This is a man with a phone
Illustration: black and white portrait of man with phone
This is a woman with a hat
Illustration: black and white portrait of woman with hat
This is a man with a beard
Illustration: black and white portrait of man with beard
This is a woman with dark hair
Illustration: black and white portrait of woman with dark hair
What did you see first in this image?
Illustration: black and white ambiguous portrait
The sequence of images included the woman's face (image at left). When shown the woman's face before viewing the ambiguous drawing (center image), most people apply that perceptual set to the drawing and perceive a woman. But when people view the drawing of the man playing a horn (image at right) before the ambiguous drawing, they tend to see a man.
Your Answer
Illustration: black and white portrait of woman with dark hair
Your Answer
Illustration: black and white male figure playing horn
Illustration: black and white ambiguous portrait

Practice 3: Creating an Expectation about Spoken Words

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Practice 3: Creating an Expectation about Spoken Words

Follow the steps to experience the power of perceptual set.

When audio clips of a person speaking are played backwards, people sometimes report hearing "hidden messages" embedded in the random sound waves. Why does this happen?

Step 1: Select the "Play normal" button and listen to a reading from “Jabberwocky” by Lewis Carroll. (Select "View the reading" button to see this portion of the Jabberwocky poem spelled out.)

Step 2: Select the "Play backward" button and listen to the same reading in reverse, trying hard to hear any hidden messages in the form of intelligible English words or phrases. Did you hear any words or phrases?

Step 3: Select the "Perceptual set" button and read the phrase provided.

Step 4: Select the "Play backward" button again and listen to the reading in reverse one more time. Now that you have a perceptual set for what you are going to hear, does the phrase jump out at you? If so, remember that the phrase doesn't really exist. Your perceptual system has simply imposed the phrase (through top-down processing) on its interpretation of a series of completely random, meaningless sounds (generated through bottom-up processing).

Caroll, Lewis (Charles Lutwidge Dodgson). (1871). Through the looking-glass, and what Alice found there. London: Macmillan.

Vokey, J. R., & Read, J. D. (1985). Subliminal messages: Between the Devil and the media. American Psychologist, 40, 1231-1239.

Quiz 1

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Quiz 1

Match the terms to their descriptions by dragging each colored circle to the appropriate gray circle. When all the circles have been placed, select the CHECK ANSWER button.

Select the NEXT button and move to Quiz 2.
Perhaps you should go back to review how perceptual set influences perception.
perceptual set
top-down processing
bottom-up processing
using existing knowledge or beliefs to interpret the sensory information, leading to faster perception but also to errors
analysis of the raw input from the sensory systems in order to construct a perception
an expectation of what will be perceived; influences what is actually perceived

Quiz 2

mc_test

Quiz 2

Answer the question. Then select the CHECK ANSWER button.

Illustration of snake/monster in lake with mountain backdrop (accompanies text for answer choice “A”)

A. People who believe in the Loch Ness monster are likely to see the monster, whereas skeptics are likely to interpret the same visual input as floating logs or unusual wave patterns.

Illustration of flying saucer (accompanies text for answer choice “B”)

B. UFO sightings tend to occur in clusters, especially if the first reported sightings are publicized in the media.

Illustration of three people (accompanies text for answer choice “C”)

C. People who arrange to meet a friend in a public place sometimes misperceive a stranger as the person they are looking for.

You did not answer the question correctly. Try to answer the question again.
Perceptual set helps explain all of these situations. Select the NEXT button and move to the Conclusion.
Perceptual set helps explain which of the situations shown above?
A
B
C
all three situations

Conclusion

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Illustration: Bev Doolittle-style illustration with hidden figures in a landscape scene, OR a human figure in a bizarre position or location
Christophe Kiciak/Getty Images
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