Abstract
Magnitude Perception in the visual domain includes enumeration and perceptual averaging. Enumeration is a process of estimating the number of objects, while Perceptual averaging is perceiving the average value of a feature of an ensemble. In the present work, we are studying the interaction between both over a varied presentation duration. In Experiment 1, participants responded to two tasks: numerosity comparison and mean size estimation. We adapted the participants to fixed numerosity (13) and mean size(50px) of a set of black dots. The individual size of the dots and their location varied in each display. Test stimuli were varied in numerosity and mean size of different values. Participants were asked to compare either numerosity or the mean size of the set with the reference value. We obtained the point of subjective equality (PSE) for number and size trials separately. The PSE for both number and size trials were very close to 1 showing more veridical representation (F (1,42) =0.04421, p=0.3917). We concluded this was because participants were given unrestricted time to respond to the trials. In Experiment 2, we made the test stimuli appear for three different durations 68ms,500ms and 1s. For both the Enumeration and Size, PSE values are close to one for 68ms. For the test of the main effect between enumeration and size, we have conducted a 2-way ANOVA test. We have a statistically significant variance at the p=.002 level (F (1,138) =9.96, p<0.01). In Experiment 1, participants have given unrestricted time to respond to the stimulus, and the results show that they were more accurate than the second experiment in which the duration of test stimuli was restricted. From both experiments, we can conclude that both numerosity and mean size tasks depend on the presentation time for an accurate estimation.