Related Experiment Video
Updated: Aug 29, 2026

A Psychophysics Paradigm for the Collection and Analysis of Similarity Judgments
Published on: March 1, 2022
Comparison is not just subtraction: effects of time- and space-order on subjective stimulus difference
1Department of Psychology, Stockholm University, Stockholm, Sweden. hellst@psychology.su.se
Abstract:
In five experiments, participants made comparative judgments of paired successive or simultaneous stimuli. Time- or space-order errors were obtained, which varied with the interstimulus interval (ISI) or stimulus duration, as well as with the stimulus level. The results, in terms of scaled subjective differences, are well described by Hellström's (1979) sensation-weighting model. With successive presentation, in comparisons of line length and tone loudness, the first stimulus had the greater weight in determining the subjective difference for short ISIs, the second for longer ISIs. In comparisons of duration (auditory and visual), the second stimulus had the greater weight. For simultaneously presented line lengths, the left stimulus had the greater weight.
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