Effects of Stimulus Order on Comparative Judgments Across Stimulus Attributes and Sensory Modalities

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In psychophysical experiments, participants are often asked to compare the magnitude of a constant standard against the magnitude of a variable comparison. According to prominent models of stimulus discrimination, discrimination sensitivity should depend only on the physical magnitude difference between these two stimuli but not on the order of their presentation. However, previous experiments on auditory duration discrimination have shown that discrimination sensitivity is higher when the standard precedes rather than follows the comparison. It is presently unclear whether this Type B effect emerges only for duration discrimination or generalizes across modalities and stimulus attributes. Therefore, we conducted a study in which participants performed several discrimination tasks for various stimulus attributes (i.e., duration, frequency, intensity, and numerosity), each in the visual and in the auditory modality. In all cases, discrimination sensitivity was higher when the standard preceded rather than followed the comparison. This result indicates that the Type B effect is not restricted to the domain of temporal cognition but rather reflects a general phenomenon across a range of domains and modalities. The outcome of the present experiment is consistent with the internal reference model according to which the Type B effect is a consequence of a dynamically updated internal reference, which is used in the comparison process. Alternatively, a weighted difference model with a larger weight for the second stimulus position than for the first stimulus position can also account for this result.

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