Variability of dot spread is overestimated

Jessica K. Witt, Mengzhu Fu, Michael D. Dodd

Research output: Contribution to journalArticlepeer-review


Previous research has demonstrated that individuals exhibit a tendency to overestimate the variability of both low-level features (e.g., color, orientation) and mid-level features (e.g., size) when items are presented dynamically in a sequential order, a finding we will refer to as the variability overestimation effect. Because previous research on this bias used sequential displays, an open question is whether the effect is due to a memory-related bias or a vision-related bias. To assess whether the bias would also be apparent with static, simultaneous displays, and to examine whether the bias generalizes to spatial properties, we tested participants’ perception of the variability of a cluster of dots. Results showed a consistent overestimation bias: Participants judged the dots as being more spread than they actually were. The variability overestimation effect was observed when there were 10 or 20 dots but not when there were 50 dots. Taken together, the results of the current study contribute to the ensemble perception literature by providing evidence that simultaneously presented stimuli are also susceptible to the variability overestimation effect. The use of static displays further demonstrates that this bias is present in both dynamic and static contexts, suggesting an inherent bias existent in the human visual system. A potential theoretical account—boundary effect—is discussed as a potential underlying mechanism. Moreover, the present study has implications for common visual tasks carried out in real-world scenarios, such as a radiologist making judgments about distribution of calcification in breast cancer diagnoses.

Original languageEnglish (US)
Pages (from-to)494-504
Number of pages11
JournalAttention, Perception, and Psychophysics
Issue number2
StatePublished - Feb 2023
Externally publishedYes


  • Ensemble perception
  • Perceived spread
  • Variability
  • Visual biases

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Language and Linguistics
  • Sensory Systems
  • Linguistics and Language


Dive into the research topics of 'Variability of dot spread is overestimated'. Together they form a unique fingerprint.

Cite this