Ensemble representations: Effects of set size and item heterogeneity on average size perception

Alexander P. Marchant, Daniel J. Simons, Jan W. de Fockert

Research output: Contribution to journalArticlepeer-review


Observers can accurately perceive and evaluate the statistical properties of a set of objects, forming what is now known as an ensemble representation. The accuracy and speed with which people can judge the mean size of a set of objects have led to the proposal that ensemble representations of average size can be computed in parallel when attention is distributed across the display. Consistent with this idea, judgments of mean size show little or no decrement in accuracy when the number of objects in the set increases. However, the lack of a set size effect might result from the regularity of the item sizes used in previous studies. Here, we replicate these previous findings, but show that judgments of mean set size become less accurate when set size increases and the heterogeneity of the item sizes increases. This pattern can be explained by assuming that average size judgments are computed using a limited capacity sampling strategy, and it does not necessitate an ensemble representation computed in parallel across all items in a display.

Original languageEnglish (US)
Pages (from-to)245-250
Number of pages6
JournalActa Psychologica
Issue number2
StatePublished - Feb 2013


  • 2323 Visual Perception
  • 2340 Cognitive Processes
  • 2346 Attention
  • Average size
  • Ensemble representations
  • Sampling
  • Set size
  • Statistical processing

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Developmental and Educational Psychology
  • Arts and Humanities (miscellaneous)


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