Primary academic research into the visual phenomena of "pop-out" and "ensemble perception" and their effect on visual short-term memory.
In the present study, we examine how visual pop-out skews ensemble perception. Participants viewed ensembles of differently-sized circles containing a single circle with a task-irrelevant pop-out feature (color or luminance). Then, participants estimated the average size of the circles shown. We found that the task-irrelevant pop-out of a single circle biases
participants’ estimations of the mean size of a group of circles towards the size of the pop-out circle. Our findings suggest that ensemble statistical summary representations in visual short-term memory (VSTM) are affected by pop-out, and that this may occur via the hierarchical processing model proposed by Brady & Alvarez (2011).
Figure 1. Figure 1 contains a cascade showing a sampling of experimental frames: first, a stimulus arrangement appears for 1500ms, followed by a response frame until the subject responds, and then the next stimulus frame appears. This pattern continues for the entirety of the experiment, divided into 20-frame (10 experimental frames, 10 response frames) blocks.
Figure 2 contains three rows. The first row shows examples of the possible arrangements for the “color” condition. The first contains an example of the “small” arrangement (i.e. 2 of the smallest size circles are present), the second contains an example of the “medium” arrangement (i.e. one of each size circle), and the third contains an example of the “large” arrangement (i.e. 2 of the largest size circles are present). The second row contains the same arrangements, but for the “luminance” condition. The final row contains an example of the 3 configurations for response frames (these examples are all designed to follow the “large” arrangement experimental frames).
This table shows the p-values for Welch Two-Sample t-tests between the bias numbers for small and large popout conditions and between the bias numbers for medium popout conditions and control conditions. The top portion of the table shows these values within the “color” conditions, the middle portion of the table shows these values within the “luminance” conditions, and the final portion of the table shows these values across all trials. The symbol (*) indicates significance (p < 0.05).