Conclusion

In this target article I have stressed several points. The first is the remarkable degree of similarity in the capacity limit in working memory observed with a wide range of procedures. A restricted set of conditions is necessary to observe this limit. It can be observed only with procedures that allow assumptions about what the independent chunks are, and that limit the recursive use of the limited-capacity store (in which it is applied first to one kind of activated representation and then to another type). The preponderance of evidence from procedures fitting these conditions strongly suggests a mean memory capacity in adults of 3 to 5 chunks, whereas individual scores appear to range more widely from about 2 up to about 6 chunks. The evidence for this pure capacity limit is considerably more extensive than that for the somewhat higher limit of 7 + 2 stimuli; that higher limit is valid nevertheless as a commonly observed, compound STM limit for materials that allow on-line rehearsal, chunking, and memorization, for which the exact number of chunks in memory cannot be ascertained. The fundamental capacity limit appears to coincide with conditions in which the chunks are held in the focus of attention at one time; so it is the focus of attention that appears to be capacity-limited.

When the material to be remembered is diverse (e.g., some items spoken and some printed; some words and some tones; or some verbal and some nonverbal items), the scene is not coherent and multiple retrievals result in considerably better recall. This all suggests that the focus of attention, as a capacity-limited storage mechanism, can shift from one type of material to another or from one level of organization to another, and that the individual is only aware of the handful of separate units of a related type within a scene at any one moment (Cowan, 1995; Mandler, 1985).

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Acknowledgments

This project was supported by NICHD Grant R01 21338. I thank Monica Fabiani, Gabriele Gratton, and Michael Stadler for helpful comments. Address correspondence to Nelson Cowan, Department of Psychology, University of Missouri, 210 McAlester Hall, Columbia, MO, USA. E-mail: CowanN@Missouri.edu.

Learning & Memory
Chapter 7: Models
(pp. 192 - 214)

1. INTRODUCTION. From the time that the discipline of psychology was in its infancy, researchers have assumed that memory is compartmentalized into several different components or types of memory. For example, consider these early thoughts by William James, one of the founders of psychology in America:

On "primary memory"(James, The Principles of Psychology, 1890): "An object which is recollected, in the proper sense of that term, is one which has been absent from consciousness altogether and now revives anew....But an object of primary memory is not thus brought back; it never was lost; its date was never cut off in consciousness from that of the immediately present moment."

On "secondary memory" (James, Psychology: the Briefer Course, 1892): "Memory proper, or secondary memory, as it might be styled, is the knowledge of a former state of mind after it has already once dropped from consciousness; or rather it is the knowledge of an event, or fact, of which meantime we have not been thinking, with the additional consciousness that we have thought or experienced it before."

Since those early days, many other writers have suggested other ways to divide memory into multiple components. Is this compartmentalized view defensible? Why or why not? What does all of this have to do with heuristic value and dissociation?

1. THE STORAGE SYSTEM APPROACH: an example of compartmentalization (based on Atkinson & Shiffrin, 1968)

A sampling of evidence:

A. Visual Sensory Memory: (Averbach & Sperling, 1960)

The stimuli:50 msec presentation of 3 x 4 matrix of letters & numbers A V   S N   P   C     T
Whole report: Procedure: "Tell me everything you can remember from the entire display" Results: correct recall of most of top line Obvious Interpretation: in 50 msec, can only take in a few letters HOWEVER... Partial report: Procedure: Present matrix and play 1 of 3 tones cuing recall for one of the lines Timing of tone was varied from 100 msec before the display to 1000 msec after. Results:
	Averbach and Sperling's Conclusion: "The work described in this paper shows that the visual process involves a buffer storage of relatively high capacity that can take in information virtually instantaneously and retain it to permit its relatively slow utilization." This 'buffer' came to be known as visual sensory memory or iconic memory. The 'relatively slow utilization' came to be thought of as the transfer of items to STM.

B. STM vs LTM

· The serial position curve & double dissociation (Fig. 7.2)

· Retrograde vs. anterograde amnesic patients

· More info on the STM/LTM distinction: (Amber R., Amanda W., Bobbie P. & Cassie K)

C. Further Divisions: varieties of LTM

§ Why bother?

i. Lots of different kinds of info: autobiographical, factual knowledge, episodic, skills, conditioned responses, explicit, implicit, etc.

ii. Amnesic patients--dissociation

§ One example: episodic vs. semantic

i. "personal, time-dated, sometimes emotional & unique" or "impersonal, timeless, emotionally neutral and universal"

ii. Dan Schacter's forgetful golfer (semantic vs episodic)

iii. Endel Tulving's head-injured motorcyclist (autobiographical vs episodic)

iv. Neuropsych evidence

v. BUT...a word of warning: where do semantic memories come from?

§ Another way to cut the cake: explicit vs implicit

i. Explicit: measured by correct responses when directly asked to remember a prior event (e.g., recall or recognition)

ii. Implicit: measured by improvements in performance as a result of experience but without directly asking the subject to remember anything. Confused? Some examples may help:

o Helmholtz savings

o priming (e.g., "nurse-doctor" lexical decision task, word completion, recognition RT, fragmented words or pictures task-- Fig 7.4)

o procedural learning (e.g., Tower of Hanoi puzzle)

o list repetition:

iii. All of the above on implicit/explicit simply refers to differences in the procedures used to measure memory--implicit or explicit procedures. Does any of this justify a belief in different memory systems? (Hint: the dissociation data are summarized on p. 207)

1. QUICKIE SUMMARY:

The modal model proposes that memory consists of several different stages and storage mechanisms, and how well you can remember an experience depends on which "box" in which you placed the information. Supporting this are data from lots of dissociation studies which find that logical differences in types of memories (i.e., episodic vs. semantic) correspond w/ differences in actual performance. There is some difference of opinion about just how to parse memory, but near consensus on the idea that it is not monolithic.

1. THE STAGE APPROACH: ENCODING - STORAGE - RETRIEVAL
   
1. Dissociation 1: the alcohol study (Table 7.3) Amanda G has more on this.
2. Dissociation 2: visual priming (Figure 7.4): normal adults vs Alzheimer's patients

1. AND NOW, FOR SOMETHING COMPLETELY DIFFERENT: PROCESSING APPROACHES

A. Consider the following experiment: DO HYDE & JENKINS SIMULATION

Hyde & Jenkins (1973) J. Verb. Lrng. & Verb. Beh:

Procedure o Auditory presentation of a 24-word list, 3 sec per word o 6 groups--each w/ a different set of instructions: § pleasantness ratings § frequency of usage § E-G checking § parts of speech § sentence frames § intentional memory o Final, unexpected free recall of the 24 words

Results:

W/in the framework of the Modal Model, why should judging the pleasantness of a word produce recall equal to (actually, a bit better than) intentional rehearsal? Answer: it shouldn't. So---what gives here?

B. Levels of Processing:

Craik & Lockhart (J. Verb. Lrn. & Verb. Beh, 1972) From pp 675-677: ASSUMPTION I: Processing ą Perception "Many theorists now agree that perception involves the rapid analysis of stimuli at a number of levels or stages... Preliminary stages are concerned with the analysis of such physical or sensory features as lines, angles, brightness, pitch, and loudness, while later stages are more concerned with matching the input against stored abstractions from past learning; that is, later stages are concerned with pattern recognition and the extraction of meaning. This conception of a series or hierarchy of processing stages is often referred to as 'depth of processing' where greater 'depth' implies a greater degree of semantic or cognitive analysis. After the stimulus has been recognized, it may undergo further processing by enrichment or elaboration. For example, after a word is recognized, it may trigger associations, images or stories on the basis of the subject’s past experience with the word...." ASSUMPTION II: (deeper processingą longer retention; memory = by-product of perceptual processing) "One of the results of this perceptual analysis is the memory trace. Such features of the trace as its coding characteristics and its persistence thus arise essentially as byproducts of perceptual processing....Specifically, we suggest that trace persistence is a function of depth of analysis, with deeper levels of analysis associated with more elaborate, longer lasting, and stronger traces.... It is perfectly possible to draw a box around early analyses and call it sensory memory and a box around intermediate analyses called short-term memory, but that procedure both oversimplifies matters and evades the more significant issues...." "Thus, we prefer to think of memory tied to levels of perceptual processing. Although these levels may be grouped into stages (sensory analyses, pattern recognition, and stimulus elaboration, for example) processing levels may be more usefully envisaged as a continuum of analysis. Thus, memory, too, is viewed as a continuum from the transient products of sensory analyses to the highly durable products of semantic-associative operations. ASSUMPTION III: (rehearsal = continued processing; maintenance & elaborative) "...superimposed on this basic memory system there is a second way in which stimuli can be retained—by recirculating information at one level of processing. In our view, such descriptions as 'continued attention to certain aspects of the stimulus,' 'keeping the items in consciousness,' 'holding the items in the rehearsal buffer,' and 'retention of the items in primary memory' all refer to the same concept of maintaining information at one level of processing.... This Type I processing, that is, repetition of analyses which have already been carried out [ maintenance rehearsal ], may be contrasted with Type II processing which involves deeper analysis of the stimulus [ elaborative rehearsal ]. Only this second type of rehearsal should lead to improved memory performance. To the extent that the subject utilizes Type II processing, memory will improve with total study time..." SUMMARY: "To summarize, it is suggested that the memory trace is better described in terms of depth of processing or degree of stimulus elaboration. Deeper analysis leads to a more persistent trace. While information may be held in PM [Primary or Working Memory], such maintenance will not in itself improve subsequent retention; when attention is diverted, information is lost at a rate which depends essentially on the level of analysis...."

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http://www.scottsdalecc.edu/ricker/psy101/readings/Section_4/4-1.html