Miller (1956) summarized evidence that people can remember about seven chunks in short-term memory (STM) tasks. However, that number was meant more as a rough estimate and a rhetorical device than as a real capacity limit. Others have since suggested that there is a more precise capacity limit, but that it is only three to five chunks. The present target article brings together a wide variety of data on capacity limits suggesting that the smaller capacity limit is real. Capacity limits (...) will be useful in analyses of information processing only if the boundary conditions for observing them can be carefully described. Four basic conditions in which chunks can be identified and capacity limits can accordingly be observed are: (1) when information overload limits chunks to individual stimulus items, (2) when other steps are taken specifically to block the recoding of stimulus items into larger chunks, (3) in performance discontinuities caused by the capacity limit, and (4) in various indirect effects of the capacity limit. Under these conditions, rehearsal and long-term memory cannot be used to combine stimulus items into chunks of an unknown size; nor can storage mechanisms that are not capacity-limited, such as sensory memory, allow the capacity-limited storage mechanism to be refilled during recall. A single, central capacity limit averaging about four chunks is implicated along with other, noncapacity-limited sources. The pure STM capacity limit expressed in chunks is distinguished from compound STM limits obtained when the number of separately held chunks is unclear. Reasons why pure capacity estimates fall within a narrow range are discussed and a capacity limit for the focus of attention is proposed. Key Words: attention; enumeration; information chunks; memory capacity; processing capacity; processing channels; serial recall; short-term memory; storage capacity; verbal recall; working memory capacity. (shrink)

Commentators expressed a wide variety of views on whether there is a basic capacity limit of 3 to 5 chunks and, among those who believe in it, about why it occurs. In this response, I conclude that the capacity limit is real and that the concept is strengthened by additional evidence offered by a number of commentators. I consider various arguments why the limit occurs and try to organize these arguments into a conceptual framework or “metatheory” of storage capacity limits (...) meant to be useful in future research to settle the issue. I suggest that principles of memory representation determine what parts of the representation will be most prominent but that limits of attention (or of a memory store that includes only items that have been most recently attended) determine the 3- to 5-chunk capacity limit. (shrink)

We discuss potential benefits of research in which attention is directed toward or away from a spoken channel and measures of the allocation of attention are used. This type of research is relevant to at least two basic, still-unresolved issues in cognitive psychology: the extent to which unattended information is processed and the extent to which unattended information that is processed can later be remembered. Four recent studies of this type that address these questions in various ways are reviewed as (...) illustrations. We conclude from these studies that unattended information appears to be partially processed automatically, though attention enhances the processing considerably, and the unattended information that is processed may not be retrievable in direct or many indirect memory tasks, though it remains possible that there is an automatically stored memory trace. (shrink)

Wainwright and Reingold presented equations for various versions of the process dissociation procedure that has been used to separate conscious and unconscious memory processes. In the present reply it is suggested that these equations, though helpful, may not capture some of the key theoretical possibilities that could help to resolve apparent contradictions and paradoxes in the empirical literature. Specifically, there could be an independence ofprocessesthat might be estimated to a sufficient degree of accuracy for some theoretical purposes despite a violation (...) of the assumption ofstochasticindependence. (shrink)

The present commentary agrees with many of the points made by Ruchkin et al., but brings up several important differences in assumptions. These assumptions have to do with the nature of the capacity limit in working memory and the possible bases of working-memory activation.

Blair describes fluid cognition as highly related to working memory and executive processes, and dependent on the integrity of frontal-lobe functioning. However, the literature review appears to neglect potential contributions to fluid cognition of the focus of attention as an important information-storage device, and the role of posterior brain regions in that kind of storage. Relevant cognitive and imaging studies are discussed. (Published Online April 5 2006).

Halford et al. have sharpened the concept of processing capacity as applied to various complex tasks. This commentary examines the apparent contradiction between capacity theories and theories in which it is processing speed, rather than capacity, that presumably limits cognitive performance. It explains how capacity and speed often are interrelated and suggests how one might examine whether capacity or speed is the more elementary in processing.