RESEARCH ARTICLE The Impact of Attention on Judgments of Frequency and Duration

Previous studies that examined human judgments of frequency and duration found an asymmetrical relationship: While frequency judgments were quite accurate and indepen-dent of stimulus duration, duration judgments were highly dependent upon stimulus fre-quency. 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 dumb-bell vs. relaxing the arm). Participants processed stimuli with varying presentation frequen-cies 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 pro-cessed 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 dura-tion 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 ef-fort. 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 pro-cessing 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 fre-quency and duration are suggested