Mental Measurement of Line Length: The Role of the Standard

Document Type



Psychology (Scripps)

Publication Date



Cognitive Psychology | Psychology | Social and Behavioral Sciences


Four experiments (55 undergraduates) examined RTs for magnitude estimates of line length. In the 1st 2 experiments RTs increased linearly with judged length. This result is consistent with the hypothesis that judgments are made by laying off a mental image of the standard along the line to be judged. The slope of the function relating judged length to RTs was not affected by the length of the standard line, suggesting that the rate at which the image of the standard is laid off is not a function of the length of the standard. RTs also increased linearly with judged length when Ss judged line length for a standard of 1 inch but not as well as when no standard was suggested. The hypothesized laying-off process was compared to other cognitive manipulations, such as mental rotation and size scaling. Equivalence of judgments based on the representation of the standard in perceptual memory and in imagination is discussed.

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© 1981 American Psychological Association

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