Attention, Perception, & Psychophysics

, Volume 80, Issue 8, pp 2033–2047 | Cite as

Capacity limit of ensemble perception of multiple spatially intermixed sets

  • Anna Xiao LuoEmail author
  • Jiaying Zhao


The visual system is remarkably efficient at extracting summary statistics from the environment. Yet at any given time, the environment consists of many groups of objects distributed over space. Thus, the challenge for the visual system is to summarize over multiple groups. The current study investigates the capacity and computational efficiency of ensemble perception, in the context of perceiving mean sizes of multiple spatially intermixed groups of circles. In a series of experiments, participants viewed an array of one to eight sets of circles. Each set contained four circles in the same colors, but with different sizes. Participants estimated the mean size of a probed set. The set that would be probed was either known before onset of the array (pre-cue condition) or afterwards (post-cue condition). By comparing estimation error in the pre-cue and post-cue conditions, we found that participants could reliably estimate mean sizes for approximately two sets (Experiment 1). Importantly, this capacity was robust against attention bias toward individual objects in the sets (Experiment 2). Varying the exposure time to stimulus arrays did not increase the capacity limit, suggesting that ensemble perception could be limited by an internal resource constraint, rather than the speed of information encoding (Experiment 3). Moreover, we found that the visual system could not encode and hold more individual items than ensemble representations (Experiment 4). Taken together, these results suggest that ensemble perception provides an efficient way of information processing but with constraints.


Perceptual organization Visual working memory Selective attention 



We thank Ru Qi Yu and Yu Luo for assistance in data collection. For helpful conversations, we thank Jim Enns, Lisa Feigenson, and the Zhao Lab. This work was supported by NSERC Discovery Grant (RGPIN-2014-05617 to J.Z.), the Canada Research Chairs program (to J.Z.), and the Leaders Opportunity Fund from the Canadian Foundation for Innovation (F14-05370 to J.Z.).


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Copyright information

© The Psychonomic Society, Inc. 2018

Authors and Affiliations

  1. 1.Department of PsychiatryUniversity of British ColumbiaVancouverCanada
  2. 2.Department of PsychologyUniversity of British ColumbiaVancouverCanada
  3. 3.Institute for Resources, Environment and SustainabilityUniversity of British ColumbiaVancouverCanada

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