Chapter 1. Size Constancy

1.1 Background

Cognitive Tool Kit
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Size Constancy

As an object gets farther away from us, the size of the image of that object on the retina shrinks. Take a look at the figure below.

The two arrows at the top of the figure are exactly the same size, but the more distant arrow will cast a smaller image on the retina, as indicated by the two arrows at the bottom of the figure (drawn to the relative sizes of their images on the retina).

If we saw the world in a way that depended upon the retinal image size, your friends would shrink rapidly as they walked away from you. Their height would halve with each doubling of distance. At 4 feet, they would appear to be half the size or 2 feet. Take a look at the following photograph.

Fortunately, this photograph does not illustrate the way we view the world. We have size constancy, which is the perception that objects stay about the same size despite their different distances from us and the different retinal images they cast. Our depth perception plays a critical role in size constancy and this experiment will illustrate that.

References:

Boring, E. G. (1964). Size constancy in a picture. The American Journal of Psychology, 77(3), 494-498.

Holway, A. H., & Boring, E. G. (1941). Determinants of apparent visual size with distance variant. The American Journal of Psychology, 54, 21-37.

1.2 Experiment Setup

1.3 Instructions

You will be asked to adjust the size of the figure on the right so that it appears to be exactly the same size as the figure on the left. When the figures look to be the same size, press the Match button to move to the next trial.

Keyboard Responses

Key What Response Means
+ or = (same key) Increase the size of the left figure
- Decrease the size of the right figure

1.4 Experiment

1.5 Results

1.6 Quiz

Question 1.1

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1
Correct.
Incorrect.
The independent variable is the value that is changed by the experimenter. In this case, the number of depth cues present was manipulated.

Question 1.2

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1
Correct.
Incorrect.
The dependent variable is the value that the experimenter collects to indicate how you performed in the experiment. In this case, we recorded the size of the left-hand figure when you pressed the match button. So, the correct answer is the size of the left-hand figure.

Question 1.3

WAhUyOvCtdSX+/fMgQroyaGcnPdzGCzMIk5MA2ScEZdof8zaFuo12YRy30ATcUT5+8Qr6MP/7qRLj8D4TvkeKYmxReVh+AXHsQSi8hAIhDC7NGb5koeYyob/zAlWVCmw2qhalB6dnm3J30apppMhWFHOUXSaJTHQkSGrRcPP7cSMf3SWtBLGEon8stc0h2JUKy7a3F/tkVgg35By4wsLAgHY4hJuEleIIbo3QIxfhldSb1ZgB/BwQl/CP4cdTC1qr+aGFBoSnZ4OwiZ4Am6DGh/9bH9UTmFjYvvTShOCmxs5Ztpu
1
Correct.
Incorrect.
This experiment examines reasons that we see objects of the same actual size as having the same size despite changes in the size of the retinal image. As a result, this phenomenon is called size constancy.

Question 1.4

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1
Correct.
Incorrect.
Generally, the more depth cues, the better our size constancy.

Question 1.5

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1
Correct.
Incorrect.
As an object gets farther from you, it takes up less area on your retina.