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The Psychophysics of Mental Test Difficulty

Published online by Cambridge University Press:  01 January 2025

J. P. Guilford
J. P. Guilford*
Affiliation:
University of Nebraska
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Abstract

By the use of the Seashore tests of Pitch Discrimination, Intensity Discrimination, Time Discrimination, and the test of Tonal Memory, it is shown that the easiness of an item, as determined by absolute scaling methods, is proportional to the logarithm of the magnitude of the stimulus. It is proposed that this is a case of Fechner's psychophysical law and that the unit of absolute scaling as applied to test items may become a satisfactory unit of all S-scales in the more traditional psychophysical problem.

Type
Original Paper
Information
Psychometrika , Volume 2 , Issue 2 , June 1937 , pp. 121 - 133
Copyright
Copyright © 1937 The Psychometric Society

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References

* For the use of these data I am indebted to Miss Kathleen Carter who gives the proportions of correct judgments for every level of difficulty of item in a Master’s thesis entitled “A weighted scoring scale for the Seashore tests of musical ability,” 1934, on file in the University of Nebraska Library.

† P. R. Farnsworth. “A critical study of the Seashore-Kwalwasser test battery,” Genet. Psychol. Monog., 1931, 9, 291-393.

‡ J. P. Guilford. “The determination of item difficulty when chance success is a factor,” Psychometrika, 1936, 1, 259-264.

* Proportions of .500, or ones slightly less like the two in this table, lead to scale values of minus infinity, a scale value that is theoretically reserved for stimulus differences of zero. It has been assumed that the proportions of .488 and .471 are due to sampling errors. In groups of only 100 subjects a reasonable lower limit for S here is about —2.000, and that assumption has been made.

* For a brief description of the absolute scaling processes and their underlying principles, see J. P. Guilford, Psychometric Methods. New York: McGraw- Hill, 1936, 440-443.

* It is to be questioned whether all ten melodies of equal length are really equal in difficulty since the melodies themselves differ in slope, in form, and in the position of the altered tone. But we may assume that the average difficulty of a set of ten of the same length is a representative level for that number of tones.

* L. L. Thurstone, The phi-gamma hypothesis, J. Exper. Psychol, 1928, 11, 293-305.