Variability in encoding precision accounts for visual short-term memory limitations

Ronald Van Den Berg, Hongsup Shin, Wen Chuang Chou, Ryan George, Wei Ji Ma

Research output: Contribution to journalArticlepeer-review


It is commonly believed that visual short-term memory (VSTM) consists of a fixed number of "slots" in which items can be stored. An alternative theory in which memory resource is a continuous quantity distributed over all items seems to be refuted by the appearance of guessing in human responses. Here, we introduce a model in which resource is not only continuous but also variable across items and trials, causing random fluctuations in encoding precision. We tested this model against previous models using two VSTM paradigms and two feature dimensions. Our model accurately accounts for all aspects of the data, including apparent guessing, and outperforms slot models in formal model comparison. At the neural level, variability in precision might correspond to variability in neural population gain and doubly stochastic stimulus representation. Our results suggest that VSTM resource is continuous and variable rather than discrete and fixed and might explain why subjective experience of VSTM is not all or none.

Original languageEnglish (US)
Pages (from-to)8780-8785
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number22
StatePublished - May 29 2012


  • Attention
  • Bayesian inference
  • Change localization
  • Estimation
  • Working memory

ASJC Scopus subject areas

  • General


Dive into the research topics of 'Variability in encoding precision accounts for visual short-term memory limitations'. Together they form a unique fingerprint.

Cite this