(The background to this 10 part series is here.  We need your comments / peer review to make this primer on education theory better.   We will acknowledge your contribution in the forthcoming eBook. 

-Jonathan (@sherbino))

Modal Model of Memory

Authors: Sylvia Alden (@salden505), Rachel Dahms (@radahms), Emily Rose

Editor: Michael Gottlieb (@MGottliebMD)

Main Authors or Originators: Richard Atkinson and Richard Shiffrin

Other important authors: Alan Baddeley

Part 1:  The Hook

Joan is a second year Emergency Medicine resident with severe test anxiety. She consistently struggled with passing her examinations in medical school, which frustrated her, as she was always able to memorize things quickly. Throughout college and medical school, she would study by cramming for hours the night before an exam. She often would perform well on small quizzes with this approach, but always struggled with her final exams. She wants to remember everything for her upcoming in-service exam, which she did very poorly on during her first year. She is seeking advice to improve her study techniques to facilitate better long-term retention.

What is the best method to study the material?

Part 2:  The Core

Overview

The modal model of memory suggests that the human memory has three separate components:

1. Sensory register: where information initially enters via the five senses

2. Short-term memory (STM): the ‘working memory’ where information from both the sensory register and long-term memory is processed

3. Long-term memory (LTM): a long-term storage area that holds information that has been rehearsed in the STM

As the STM has finite capacity and requires significant energy requirements, not all sensory information is attended to. Therefore, the content of the STM is significantly smaller than that of the sensory register. The sensory register is the sum of all input, whereas the STM is what you pay attention to, or consciously think about. The STM can hold between 4-10 discrete pieces of information at a time. There is a constant transition of items from STM to LTM. Items are moved into LTM based on the amount of time they are kept in the STM. As new items are introduced into the STM, the oldest items are lost after the capacity has been reached. If these items have moved into LTM, they are retrievable. Long term memory is indefinite, serving as a permanent store of information. However, if the information has been replaced in the STM before moving into LTM, these items are lost and not retrievable (i.e. not learned).

Background

The earliest reference to modal memory (i.e. the idea that there are separate, though interconnected, memory stores) was by William James in 1890.1 He described primary memory as momentary, conscious memory and secondary memory as permanent, unconscious memory. The observation that heralded the modern theory of modal memory was that a short sequence of items will be forgotten if rehearsal is interrupted by a distraction. Although there were many contemporaneous descriptions of this theory of memory, Atkinson and Shiffrin gave the most complete description in 1968.1 They were also the first to add a third aspect to this theory: sensory register.

Modern takes or advances

One of the most influential models to arise out of the initial Atkinson & Shiffrin theory is Alan Baddeley’s Working Memory Model.1,2 This model postulates that instead of a single, limited-capacity STM that passively stores information, there is a multi-component active processing system. This model is composed of a supervisory system (i.e. central executive system) and two slave systems (i.e. the phonological loop and the visuospatial sketchpad).

The central executive system is in charge of strategy selection and integration from various sources including the phonological loop and visuospatial sketchpad. It is responsible for attentional control. The phonological loop stores information with sub-vocal rehearsal (i.e. internal, silent dialogue). If information is not rehearsed in such a manner, the data will decay within seconds. Inputs into this loop include both the internal dialogue and external auditory input surrounding an encounter. The visuospatial sketchpad involves both visual and spatial processing that are separate from the verbal processing of the phonological loop.

Another theory derived from the modal model of memory is that of conceptual short-term memory. Conceptual STM is used for sentence processing, everyday reading, and scene perception.1,3 It is postulated that when presented with a visual stimulus, such as a sentence, the information simultaneously goes into the phonological loop, as well as the conceptual STM. This area of memory can hold large amounts of information, although it decays very quickly unless it is relevant to an existing conceptual structure that is organized into and stored in LTM.

Search of Associative Memory is a theory put forth by Raaijmakers and Shiffrin in 1981 that addresses retrieval from LTM.1,4,5 It is based on the idea that events are encoded in memory as separate “packages” that can be accessed via retrieval cues. The strength of the cue will be determined by pre-existing relationships, as well as rehearsal and coding performed in the STM. In other words, two images are linked together by rehearsing them in conjunction with each other. Therefore, recall from the LTM is based on cues originating from the subject, with each cue assigned different value based upon the degree of salience. When retrieval is attempted, the memory image with the strongest cue will be recalled most easily.

Finally, Ericsson and Kintsch put forth the idea of long-term working memory in 1993 to explain why working within an area of expertise appears to allow individuals to far exceed the constraints of working memory.1,6 They proposed that skilled use of storage in long-term working memory can be combined with temporary storage in short-term working memory. They felt that retrieval cues made well-known information much faster to retrieve, and allowed active manipulation of this information to supersede the rules of working memory. Specifically, they suggest that there is minimal effect from interruption; interrupting a reading test does not dramatically reduce comprehension of the material prior to the interruption.

Other examples of where this theory might apply in both the classroom & clinical setting

The modal model of memory stresses the importance of actively reviewing recently encountered material in order to move it into LTM. Additionally, there is emphasis in moving information from the sensory register into the STM, which is the first step in storing the information within LTM.

In the classroom, there are several different ways to encourage this necessary repetition. One approach could be the use of planned educational sessions, followed by simulation cases based on the topics discussed in order to build repetition into the structure of the curriculum. There is also some evidence supporting the flipped classroom. This may improve information retention by requiring learners to prepare in advance for an in-class session, thereby increasing the time spent storing and recalling information in LTM.

In the clinical realm, having learners give a short presentation on a clinical entity that they recently encountered can assist in enhancing retention of the material. Bridging between the classroom and clinical learning will further assist learners in encoding information into LTM. This can be done by asking learners what they have been studying and having them to apply this new information to current clinical encounters.

Annotated Bibliography of Key Papers

Healy AF, McNamara DS. Verbal learning and memory: does the modal model still work? Annu Rev Psychol. 1996;47:143-172.

This is a review article that provides a thorough discussion of verbal learning and memory. It begins with a background of the work leading up to Atkinson and Shiffrin’s modal model of memory. This is followed by a description of the model itself and discussion of the research supporting and refuting the model. Finally, the authors discuss extensions and alternative theories to the model. This article serves as a great starting point for the reader interested in a more in-depth overview of this model.

Baddeley A. Working Memory. Comptes rendus de l’Academie des sciences. Serie III, Sciences de la vie. 1998;321(2-3):167-73

This article discusses one of the most influential theories derived from the original modal model of memory, the concept of working memory. Working memory is a system for the temporary storage and manipulation of information. This publication details the history of the analysis of the functional structure of human memory and the associated controversies. It presents the background behind the development of the three-component model (i.e. the central executive system, the visuospatial sketchpad, and phonological loop).

Smith AM, Floerke VA, Thomas AK. Retrieval practice protects memory against acute stress. Science. 2016 Nov;354(6315):1046-8.

This study compared retrieval practice (RP) with standard study (SS) techniques (i.e. repeatedly restudying the same material) for recall during stressful scenarios. Participants were randomized to RP and SS groups and then quizzed 24 hours later in both stressed and non-stressed environments. The stressed RP group performed similarly to both non-stressed groups (i.e. RP and SS) and significantly better than the stressed SS group. The authors suggest that using RP can counteract the decreased memory response noted during stressful scenarios.

Limitations

In 1972, Craik and Lockhart noted that the encoding of information from STM to LTM is not solely dictated by the time spent in rehearsal, but also depends on the amount and depth of attention. Rehearsal at a shallow level (i.e. Type 1 Processing) will result in a higher rate of forgetting than Type 2 Processing.1,8 They defined Type 1 processing as repetition without analysis, whereas Type 2 processing consists of deep rehearsal with analysis of the stimulus. As an example, repeating “albuterol treats asthma” for three minutes would be considered Type 1 processing, whereas thinking about how albuterol, as a ß-agonist, binds with ß2 receptors in the smooth muscle of the airways and reduces bronchoconstriction in the lungs, would be considered Type 2 processing.

Additionally, the modal model of memory assumes that all LTM is permanent and that any perceived loss of information from this store is just a problem with retrieval.1,9 However, there appears to be some degree of information that is lost when it is not regularly rehearsed.1,10 Of note, this can be minimized when the person has expert-level knowledge of the material. For example, the average physician may not recall much of the Krebs cycle several years after medical school. However, a physician with extensive prior experience in metabolic research, would be far more likely to retain the same information, even if she did not use it in her current career.

Part 3:  The Denouement

Joan chose to focus her initial efforts on infectious diseases, the material she was least comfortable with, and targeted her energy on learning and retaining this material. She decided to exercise the practice of rehearsal with information. She started with a brief board review chapter on the topic, worked through some practice cases, and then dove deeper into a book chapter review of the topic. She assembled notes for herself to review later using tables and graphs. Subsequently, she reviewed her prior patient visit list for those with infectious diseases. She reviewed the clinical presentation, the diagnosis, the pathophysiology, and the management for each patient’s case. Finally, she created quizzes and consistently exercised retrieval practice to improve her recall during stressful scenarios. She realized that when she returned to the information and reviewed it on subsequent days, she recalled and understood it much better than with her prior approach of quick memorization. Once she had finished a subject, she moved on to another topic, but made sure that she spent sufficient time delving into each subject, as well as rehearsing material she had previously mastered to improve her recall. She enjoyed learning with this approach and her score significantly improved on this year’s in-service exam. She also felt stronger and more confident with each topic in the clinical arena.

PLEASE ADD YOUR PEER REVIEW IN THE COMMENTS SECTION BELOW

References

1. Healy AF, McNamara DS. Verbal learning and memory: does the modal model still work? Annu Rev Psychol. 1996;47:143-172.
2. Baddeley A. Working Memory. Comptes rendus de l’Academie des sciences. Serie III, Sciences de la vie,1998; 321(2-3), 167-73.
3. Potter M. Very short-term conceptual memory. Memory & Cognition. 1993; 21(2): 156-161.
4. Raaijmakers J, Shriffin R. Search of associative memory. Psychological Review. 1981; 88(2): 93-134.
5. Raaijmakers J. The story of the two-store model of memory: past criticisms, current status, and future directions. In Attention and Performance XIV. Cambridge, MA: MIT Press; 1993:467-488.
6. Ericsson K, Kintsch W. Long-term working memory. Psychological Review.1995; 102(2): 211-245.
7. Baddeley A. Working Memory: Theories, Models, and Controversies. Annu Rev Psychol. 2012; 63(1): 1-29.
8. Craik F, Lockhart R. Levels of processing: a framework for memory research. Journal of Verbal Learning and Verbal Behavior. 1972; 11: 671-684.
9. Bahrick H. Semantic memory content in permastore: fifty years of memory for Spanish learned in school. Journal of Experimental Psychology. General. 1984; 113(1): 1-29.
10. Squire L. On the course of forgetting in very long-term memory. Journal of Experimental Psychology. Learning, Memory and Cognition. 1989; 15(2): 241-245.