Does grouping interfere with automatic averaging?

Abstract

Ensemble perception is the visual system’s ability to extract statistical information from objects in a brief glance. The goal of this study was to see if grouping would interfere with the automatic extracting of the average orientation of lines when stimuli were presented in the periphery. That is if grouping individual lines into different letter manipulations would increase the average adjustment error. Observers were asked to report the average orientation of a group of lines, that were grouped in different combinations, from random arrangement to objects, such as letters. All stimuli were presented in the visual periphery. Our results showed that the average adjustment error was higher when lines were grouped into letters than when they were unconnected or formed pseudo letters. The symmetry of letters also had an effect, symmetrical letters had lower adjustment errors than non-symmetrical ones. Symmetrical letters also had a smaller variability of adjustment error. Average response times were also slower and the average number of clicks was higher when lines formed letters. Our results supported our hypothesis that grouping does interfere with automatic averaging and that pooling models are not effective enough to improve averaging regardless of the arrangement of the lines. The automatic extracting of the average orientation of individual lines seems to be impaired when they are grouped into letters.