Abstract
Previous studies that examined human judgments of frequency and duration found an asymmetrical relationship: While frequency judgments were quite accurate and independent of stimulus duration, duration judgments were highly dependent upon stimulus frequency. A potential explanation for these findings is that the asymmetry is moderated by the amount of attention directed to the stimuli. In the current experiment, participants' attention was manipulated in two ways: (a) intrinsically, by varying the type and arousal potential of the stimuli (names, low-arousal and high-arousal pictures), and (b) extrinsically, by varying the physical effort participants expended during the stimulus presentation (by lifting a dumbbell vs. relaxing the arm). Participants processed stimuli with varying presentation frequencies and durations and were subsequently asked to estimate the frequency and duration of each stimulus. Sensitivity to duration increased for pictures in general, especially when processed under physical effort. A large effect of stimulus frequency on duration judgments was obtained for all experimental conditions, but a similar large effect of presentation duration on frequency judgments emerged only in the conditions that could be expected to draw high amounts of attention to the stimuli: when pictures were judged under high physical effort. Almost no difference in the mutual impact of frequency and duration was obtained for low-arousal or high-arousal pictures. The mechanisms underlying the simultaneous processing of frequency and duration are discussed with respect to existing models derived from animal research. Options for the extension of such models to human processing of frequency and duration are suggested.
Highlights
In everyday life, it is very rare that a given object or event is encountered only once
We report the four main effects of frequency and duration across all attention conditions: (a) the extent to which participants were sensitive to stimulus frequency, (b) the participants’ sensitivity to total presentation duration, (c) the effect of stimulus frequency on duration judgments, and (d) the effect of stimulus duration on frequency judgments
For each multilevel regression analysis, we always controlled for the nonfocal-magnitude level by entering this variable into the analyses as additional predictor
Summary
It is very rare that a given object or event is encountered only once. One meets people and comes across things (or types of things) repeatedly, and this information about the frequency of occurrence is connected with the information about the length of exposure to these events. Judgments about these two kinds of magnitudes, one countable (frequency of occurrence) and one uncountable (duration), are likely to be related. People are remarkably sensitive to the frequency and duration of stimuli [2,3,4,5,6,7,8,9,10] If these two kinds of judgments depend on a common magnitude system, there could be a mutual biasing effect. Neurophysiological research identified brain areas that are responsible for the processing of frequency as well as duration [21]
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