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The Capacity Limit of Working Memory: Continuous or Discrete?

English title The Capacity Limit of Working Memory: Continuous or Discrete?
Applicant Oberauer Klaus
Number 135002
Funding scheme Project funding
Research institution Psychologisches Institut Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Psychology
Start/End 01.10.2011 - 30.09.2014
Approved amount 256'014.00
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Lay Summary (English)

Lay summary

Working memory is a system for the temporary maintenance of information. It serves as the workbench of cognition, in that it provides access to the relevant information for the current task. Working memory has a severely limited capacity, and this capacity limit constrains our ability to deal with complex cognitive tasks such as reasoning, problem solving, planning, understanding difficult texts, or solving complicated equations.

One goal of the cognitive psychology of working memory is to characterize the limit of the system’s capacity. One class of theories states that the capacity is a fixed number of information elements (so-called “chunks”). Information given in a test of working memory either finds a free slot in the system, in which case it is retained with high accuracy, or else it is completely forgotten, and people can only guess about it. An alternative class of models assumes that every piece of information that people try to maintain in working memory is represented with a variable degree of strength. Failures of recall arise when the strength of an element falls below a threshold, or it is overshadowed by other, much stronger information. One goal of the project is to decide between these two views of working-memory capacity.

Much research on working-memory capacity is done with short-term recognition tasks, in which participants are asked to remember a small set of elements (e.g., words, or color patches) for a few seconds, and are then asked to decide for a further element whether or not it was part of the memorized set. We will therefore use short-term recognition as the main test bed for testing the relative merits of the two classes of theories. We will start by integrating three partial mathematical models of short-term recognition developed by the applicant. These models describe short-term recognition as driven by two processes: One is a quick and automatic assessment of the familiarity of the comparison stimulus, which reflects its summed similarity to all memory elements. The other is a slower process of recollection of individual memory elements, which are compared with the comparison stimulus. Dual-process theories can be regarded as an elaborate version of continuous-strength theories because at least the familiarity signal, and perhaps also the chance of successful recollection, is thought to depend on the continuous strength of memory elements.

Discrete-capacity theories of working memory derive support mostly from short-term recognition tasks with visual material (e.g., colors, shapes), whereas continuous-strength theories and dual-process theories gain support primarily from short-term recognition of verbal materials (e.g., words, letters). Our project will carry out parallel experiments with both kinds of experiments to allow a direct comparison of the merits of the competing models in both content domains. We will competitively test mathematical models assuming a discrete capacity, and models assuming continuous strength, including dual-task models, by fitting them to the data from our experiments.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants



What limits working memory capacity?
Oberauer Klaus, Farrell Simon, Jarrold Christopher, Lewandowsky Stephan (2016), What limits working memory capacity?, in Psychological bulletin, 142(7), 758-99.
Visual working memory declines when more features must be remembered for each object
Oberauer Klaus, Eichenberger Simon (2014), Visual working memory declines when more features must be remembered for each object, in Memory & Cognition, 41, 1212-1227.
An interference model of visual working memory
Oberauer Klaus, Lin Hsuan-Yu, An interference model of visual working memory, in Psychological Review.
Focused attention improves working memory: implications for flexible-resource and discrete-capacity models
Souza Alessandra, Rerko Laura, Lin Hsuan-Yu, Oberauer Klaus, Focused attention improves working memory: implications for flexible-resource and discrete-capacity models, in Attention, Perception, and Psychophysics.


Group / person Country
Types of collaboration
Prof. Stephan Lewandowsky Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Ed Awh, University of Oregon United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Weiji Ma, New York University United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Tagung experimentall arbeitender Psychologen (TeaP) Talk given at a conference A computational model of visual working memory 31.03.2014 Giessen, Germany Oberauer Klaus;
Closing Conference of the ZiF research Group: Competitive visual processing across space and time: Interactions with memory Talk given at a conference A computational model of visual working memory 17.03.2014 Bielefeld, Germany Oberauer Klaus;
Conference of the European Society of Cognitive Psychology Talk given at a conference An interference model of visual working memory 31.08.2013 Budapest, Hungary Spengler Justus; Oberauer Klaus; Peteranderl Sonja;
Australian Mathematical Psychology Meeting Talk given at a conference Modeling visual working memory 17.01.2013 Sydney, Australia Peteranderl Sonja; Spengler Justus; Oberauer Klaus;
European Working Memory Workshop Poster Modeling visual working memory 03.09.2012 Fribourg,Switzerland, Switzerland Oberauer Klaus; Peteranderl Sonja; Spengler Justus;
Portland working memory worshop Talk given at a conference Modeling visual working memory 15.08.2012 Portland, Oregon, USA, United States of America Oberauer Klaus;

Associated projects

Number Title Start Funding scheme
192204 The Cooperation of Working Memory and Long-Term Memory 01.08.2020 Project funding
134417 Working Memory: Modelling and Experiments 01.06.2011 International short research visits
143333 The focus of attention in working memory 01.02.2013 Project funding


Working memory is a system of limited capacity that is crucial for complex cognition. Un-derstanding its mechanisms will substantially advance our understanding of intelligent thinking and behavior, and the limits of cognitive ability. The first project goal is to test two kinds of theories about the nature of working-memory capacity against each other. Strength models, dominant in research on verbal (working) memory, postulate that mem-ory traces compete at recall based on their current strength; the capacity limit arises be-cause increasing the load on working memory reduces the discriminability of traces in that competition. Fixed-capacity theories, predominately developed in the literature on visual working memory, assume that working memory can hold a fixed number of representa-tional units, which are all equally accessible independent of each other. We will carry out experiments testing these theories, using comparable designs with verbal and visuo-spatial material. Much evidence speaking to the nature of working-memory capacity comes from short-term recognition paradigms (e.g., the “change detection” paradigm). The second goal therefore is to develop a computational model of short-term recognition, building on previous modelling efforts of the applicant. The model will be a dual-process model combining two sources of evidence for a recognition decision: familiarity, arising from persistent activation of repre-sentations, and recollection, arising from bindings of contents to their contexts. This class of models has been successful with verbal memoranda but has rarely been applied to vis-ual-spatial materials. The model will be experimentally tested against competing models, in particular single-process signal-detection models popular in the verbal recognition litera-ture, and single-process high-threshold models popular in the visuo-spatial recognition lit-erature. We will again carry out parallel experiments using verbal and visual-spatial mate-rial, with the aim of providing a unified model applicable in both content domains. The final goal, to be pursued in the context of a doctoral dissertation, is the application of an existing connectionist model of serial recall, the SOB model, to short-term recognition. This effort will be guided by the more abstract mathematical modelling of recognition out-lined above.