Perceiving the Size of Individual Objects in an Ensemble under Focused and Distributed Attention

Abstract

In everyday life, people are generally successful in orienting themselves in a variety of continuously perceived visual information, but our perception has serious limitations: we can clearly perceive only objects in focus, while the rest get lost or go unnoticed. The most effective way to overcome these attention limitations is to encode the summary statistics of a set, or an ensemble, of objects with some loss of quality in perception of the properties of individual objects. In the perception of large sets of objects the observer is able to accurately allocate the statistical parameters of the set, while continuing to perceive a set of individual objects, not an abstract parameter.In this study, the authors examine how perceptions of the characteristics of an individual object surrounded by other objects, forming the ensemble, is distorted under focused and divided attention. The study involved 25 students of the National Research University Higher School of Economics with normal or corrected-to-normal vision. Participants were presented with sets of 1 to 16 circles of different sizes; after that they were asked to determine the size of an individual target circle in a two-alternative forced choice. Location of the target circle was prompted either before ensemble presentation (which led to the attention being focused on a single object), or after ensemble presentation (which allowed for the attention to be distributed between all members of the ensemble). A strong effect of context on the perception of the size of the individual circle was seen, both when attention was focused and distributed. Nevertheless, in the condition of distributed attention influence of the ensemble characteristics was much more pronounced. In addition, a tendency to "compression" of perceived size of the largest objects in ensembles was found; this was also most pronounced under distributed attention. The authors attribute this trend to the unification of the feature that increases the similarity between individual objects and promotes a holistic perception of the ensemble. When attention is focused, feature unification is weaker, which allows for processing of the characteristics of individual objects.