The Impact of Attention on Judgments of Frequency and Duration

May The Impact of Attention on Judgments of Frequency and Duration Isabell Winkler 0 1 Madlen Glauer 0 1 Tilmann Betsch 0 1 Peter Sedlmeier 0 1 0 1 Chemnitz University of Technology , Chemnitz, Germany , 2 University Medical Center of Jena , Jena, Germany , 3 University of Erfurt , Erfurt , Germany 1 Academic Editor: Jose Cesar Perales, Universidad de Granada , SPAIN 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. - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors have declared that no competing interests exist. In everyday life, it is very rare that a given object or event is encountered only once. Usually, 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. Therefore, judgments about these two kinds of magnitudes, one countable (frequency of occurrence) and one uncountable (duration), are likely to be related. Consistent with the majority of research with human participants (see [1], and the contributions therein), we use the term frequency to denote the number of times a given stimulus or type of stimulus is presented within a given time interval. Typically, people are remarkably sensitive to the frequency and duration of stimuli [210]. However, if these two kinds of judgments depend on a common magnitude system, there could be a mutual biasing effect. Thus, the question arises whether people can always trust in their perception of frequency and duration. There is indeed convincing evidence for such a common magnitude system for numerical and temporal processes [2,11]. On the basis of animal research [1217] as well as investigations with human subjects [3,1820], it can be concluded that the same mechanisms are used for the processing of frequency and duration. Moreover, neurophysiological research identified brain areas that are responsible for the processing of frequency as well as duration [21]. If there really exists a common magnitude system that is used for judgments of both frequency and duration, both kinds of stimulus information should contribute to the magnitude representation. This, as already mentioned, might yield biased estimates. For example, if a stimulus is presented 10 times, short stimulus presentations might lead to lower frequency estimates compared to longer presentations of the same stimulus (with the same presentation frequency). This reasoning also holds for the other possible kind of mutual impact: If the overall stimulus duration is, say, 10 s, having presented the stimulus 10 times (with a duration of 1 s each) might lead to a higher total duration estimate than having presented it 5 times (with a duration of 2 s each). In sum, the frequency of occurrence of stimuli should have a (biasing!) effect on the judgment of their duration, and vice versa. Whereas results from animal research conform to the postulated mutual impact of the two kinds of magnitudes, to date, the results of behavioral research with human subjects are largely inconsistent with such an assumption. The usual finding has been an asymmetrical relationship between frequency and duration (e.g., [2224]), suggesting that duration judgments are influenced by the frequency of occurrence of stimuli. In contrast, frequency judgments seem not to be influenced by presentation duration [3,18,23,24]. What might the reason be for this discrepancy between results in animal studies and those in studies with human participants? One difference between the two kinds of research is immediately evident: Animals are usually exposed to stimuli that are very important to them, while the stimuli used in studies with human participants might not rouse the latters interest very much. So it is quite likely that the attention directed to experimental stimuli plays a crucial role in these kinds of judgments and is responsible for the differential results. In animal research, the stimuliusually linked with food itemscan be expected to attract a large amount of attention, whereas the stimuli used in research with humans, such as three-letter words on a computer screen, probably do not draw much of participants attention. A low level of attention toward experimental stimuli should not have a strong impact on frequency judgments because frequency processing seems to need only minimal attention (e.g., [25,26]). In contrast, adequate duration processing seems to be highly dependent on attentional resources (e.g., [27,28]). Thus, low attention to the stimuli might be responsible for the asymmetrical results in previous studies on the mutual impact of frequency and duration. In the present study, we explored this by systematically varying the amount of attention in the simultaneous processing of stimulus frequency and duration. Our main question was whether the amount of attention directed to the stimuli has a systematic impact on the extent of bias that one quantity exerts on the other. If this is the case, one should expect the usual asymmetrical results when stimuli receive a low amount of attention. However, when a high amount of attention is directed to the stimuli, the mutual impact of fr (...truncated)