Lab #3 Object Perception: Illusory Contours and the Law of Similarity
Due Tuesday, November 6th or before via MOODLE J
Relevant section of textbook: chapter 4, pp.93-98
Illusory Contours
Some figures are perceived because they are physically present in a stimulus. Others are perceived when the stimulus suggests their presence, even if they do not really exist. The latter situation describes the conditions in which illusory contours are observed. Illusory contours are borders that are perceived but are not real. Illusory contours often are perceived when the actual figure has “missing” parts that suggest it is being partially occluded. The occluding figure’s contours are perceived as brighter regions than the rest of the field, even though the figure does not really exist.
Three different illusory contour figures are presented in this demonstration. Pay attention to the characteristics of the stimulus that induce the perception of the nonexistent figure. Think about what illusory contours suggest about pattern perception and the role of the physical stimulus.
1. Describe the illusory contours you observed in the three figures.
a.
[1 mark]
b.
[1 mark]
c.
[1 mark]
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[3 marks]
2. How might Gestalt psychologists explain illusory contours?
[2 marks]
Law of Similarity
The Gestalt psychologists are known for their laws of perceptual organization. These laws identify several very basic principles that guide how the stimulus array is grouped or organized. Perhaps the most basic grouping that occurs is figure-ground relationship. That is, which parts of the stimulus array represent the background, and which parts represent objects (figures)? Within the stimuli that represent objects, where does one object end and another begin?
One of the laws of perceptual organization is the law of similarity. As its name implies, this law states that similar patterns tend to be grouped together or perceived to be part of the same, larger object. The characteristics that cause the strongest, most immediate grouping tend to be those that are basic sensory attributes that do not require a lot of interpretation, such a size, color, brightness, line orientation, etc.
In this exercise you will see how the organization of a stimulus array is affected by the similarity of the array’s individual components. Note the organization of the array prior to adding a similarity component, and then see how the organization changes as you introduce two colors or other characteristics.
1. Describe your perception of the array prior to adding color.
[1 mark]
How did your perception change when some spheres were red and others were blue?
[1 mark]
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[2 marks]
2. What do you think would happen if the balls were randomly colored red or blue, rather than using rows or columns to assign color?
[.5 mark]
Do you think grouping would still occur? Why?
[1.5 mark]
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[2 marks]
3. Describe a real-world situation in which the law of similarity could possibly contribute to your perception.
[1 mark]
2