Types of memory and models of memory

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Inf1: Intro to Cogni-ve Science Types of memory and models of memory Alyssa Alcorn, Helen Pain and Henry Thompson March 21, 2012
Intro to Cognitive Science
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1. In the lecture today A review of short-‐term memory, and how much stuff fits in there anyway 1.  Whether or not the number 7 is magic 2.  Working memory 3.  The Baddeley-‐Hitch model of memory hEp://www.cartoonstock.com/directory/s/
short_term_memory.asp March 21, 2012
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2. Review of Short-‐Term Memory (STM) Short-‐term memory (STM) is responsible for storing small amounts of material over short periods of Nme A short Nme really means a SHORT Nme-‐-‐ up to several seconds. Anything remembered for longer than this Nme is classified as long-‐term memory and involves different systems and processes. !!! Note that this is different that what we mean mean by short-‐
term memory in everyday speech. If someone cannot remember what you told them five minutes ago, this is actually a problem with long-‐term memory. While much STM research discusses verbal or visuo-‐spaNal informaNon, the disNncNon of short vs. long-‐term applies to other types of sNmuli as well. 3/21/12
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3. Memory span and magic numbers Amount of informaNon varies with individual’s memory span = longest number of items (e.g. digits) that can be immediately repeated back in correct order. Classic research by George Miller (1956) described the apparent limits of short-‐term memory span in one of the most-‐cited papers in all of psychology. He opens (dramaNcally!) “My problem is that I have been persecuted by an integer. For seven years this number has followed me around, has intruded in my most private data, and has assaulted me from the pages of our most public journals. This number assumes a variety of disguises, being someEmes a liFle larger and someEmes a liFle smaller than usual, but never changing so much as to be unrecognizable.” 3/21/12
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Memory span and magic numbers, con-nued The persecutory number in quesNon is the now-‐famous “magical number 7 plus or minus two” For STM, this means that the general span is 5-‐9 remembered items with an average of 7 “Magical number 7” was derived from research with absolute judgement tasks •  People were asked to discriminate between sNmuli varying on only ONE dimension •  For example, judging tones that vary only in their pitch He notes performance on sNmuli varying on mulNple dimensions may be quite different, giving examples illustraNng that most of the sNmuli we encounter in everyday life are of this type. ....but is 7 the number to quote when we talk about remembering more complex sEmuli like leFers, words, or digits? 3/21/12
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4. Maybe not a magic number? Memory span results were widely confirmed and replicated for many years, but (relaNvely) recent research suggests the esNmate of a magical 7 is too high •  Some researchers suggest it should be closer to 3 or 4 •  In any case, definitely less than 10! Alternately, the problem may be that Miller’s original discussion and much subsequent literature are not making the straigheorward limit they THINK they are measuring. -‐ For example, Miller’s original retrieval task and similar ones tap into both short AND long-‐term retrieval -‐ There also appears to be variaNon in the retenNon properNes for different types of informaNon See Shiffrin & Nosofsky 1994 for a review and further references. 3/21/12
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5. Stretching our short-‐term memory span (aside from whether the “magic number” is really 7 or not....) Short-‐term memory span can be “stretched” by meaningfully grouping or chunking informaNon -‐ easier to remember one year, 1918, than four numbers 1, 9, 1, 8 -‐ naturally “recode” informaNon into chunks as aid to memory! -‐ remember postcodes, phone numbers and words as units rather than lists of individual pieces Memory span for words in a sentence is significantly longer than for unrelated, context-‐less words •  About 15 words (per Brener, 1940), compared to a magical single-‐
digit number •  Constraints imposed by the rules of grammar, context, are not sufficient to explain this! (what is longest number/ text you can recall?) 3/21/12
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6. Are “Short-‐term memory” and “working memory” synonymous? In a psychology class, textbook, or elsewhere, you may have also heard about working memory. Short-‐term memory and working memory may sound iniNally similar, but their relaNonship is more complex. These are NOT interchangeable terms. •  Working memory (abbreviated to WM) is the part of memory conceived as a “mental workspace” where informaNon is temporarily maintained and manipulated. •  Short-‐term memory as discussed earlier in this lecture is more specifically concerned with storage, maintaining small amounts of informaNon (e.g. “keeping them in mind” but not manipulaNng them or processing them more deeply) 3/21/12
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STM v. WM contd. As you will see in this lecture, the disNncNon between STM and WM has evolved over Nme. Short term memory is currently conceived as one component of the larger working memory system. 3/21/12
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7. Working memory and models of memory We will consider two models of memory: •  Modal model of memory (Atkinson & Shiffrin, 1968) •  Baddeley-‐Hitch model of memory (Baddeley & Hitch 1974; and many more) Remember modelling memory to generate predic-ons and test theories •  How much of the current data from humans can the model explain? •  How well does a model explain current human behavioural data? •  What hypotheses does the model suggest? Are these confirmed/
disconfirmed by new behavioural data? Plus addiNonal benefits in that modelling a memory phenomenon or component means specifying and explaining underlying assumpNons and resolving ambiguiNes. 3/21/12
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8. The Modal Model of memory Early memory model (Atkinson & Shiffrin, 1968) proposes the following general sequence of processing steps: 1. InformaNon enters from the environment 2. Brief processing in sensory systems 3. InformaNon goes to a short-‐term store (STS) –  Passes informaNon in and out of LTM –  Workspace to perform operaNons, select/ rehearse informaNon –  Items would be learned if held in this store 4. InformaNon is output OR goes into long-‐term store (LTS) 3/21/12
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8. The Modal Model of memory From Baddeley textbook
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9. Difficul-es with the Modal Model While a simulaNon of the modal model performed well on rote-‐learning tasks, it ran into trouble when compared to some aspects of human performance. Based on the model’s connecNon of STS and LTS, we would predict.... •  A STS deficit will lead to impairment in the LTS, because the STS is key for transferring informaNon into and out of the LTS (encoding and retrieval) •  If STS is a “workspace” for manipulaNng informaNon, a STS deficit would impair a person’s ability to do complex cogniNve tasks (e.g. reasoning) 3/21/12
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9. Difficul-es with the Modal Model, contd. However, empirical evidence contradicted both predicNons (these are just two examples) •  A case in Shallice & Warrington 1970 reported a paNent with severe deficits characterisNcs of the STS, but who also had an unimpaired LTS. •  Other paNents had impaired STSs, but managed various complex tasks like taxi-‐driving or running a business (Vallar & Shallice, 1970). Clearly, the Modal Model was too simplisEc and the proposed components needed to be altered in some way. 3/21/12
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10. The Baddeley-‐Hitch model: Pu[ng the “work” in working memory..... The Baddeley-‐Hitch (abbreviated B-‐H) model of memory is in part a “response” to the shortcomings of the earlier Modal Model. Baddeley and Hitch conducted further work to try to find out more about the underlying nature and funcNons of STM (see the Memory textbook chapter 3 for the details) The new and more complex model was of working memory, and assumes that intermediate maintenance and manipulaNon of informaNon is necessary for many complex tasks, such as adding digits in one’s head. 3/21/12
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10. The Baddeley-‐Hitch model: Pu[ng the “work” in working memory..... In Alan Baddeley’s own words, “The emphasis on ‘working’ aimed to dissociate it from earlier models of STM, which were primarily concerned with storage, and to emphasize its funcEonal role as a system that underpins complex cogniEve acEviEes, a system that supports our capacity for mental work and coherent thought” (Memory, Ch 3, p43). This more complex and acNve view of memory as enabling mental work is one contradicts the way that we ooen treat memory in everyday speech-‐-‐ as a staNc photo album or filing system. 3/21/12
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11. The Baddeley-‐Hitch model of memory The B-‐H model (Baddeley, 2003): -‐ modified and updated several Nmes, remains a widespread and useful explanatory tool. -‐  different components for different types of informaNon, unlike earlier Modal model. More typically called the mulEcomponent theory The components connect to one another as shown. -‐ Arrows indicate in which direcNons informaNon can move. 3/21/12
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12. The B-‐H model components The components are : 1.  A phonological loop for processing and encoding verbal and auditory informaNon 2.  The visuo-‐spaEal sketchpad for processing/encoding visual and spaNal informaNon 3.  A central execuEve as an “aEenNonal controller” to direct the “work” performed by working memory. As we discussed in the aEenNon unit more generally, this controller selects, manipulates, and switches between pieces of informaNon. 4.  A mulN-‐dimensional episodic buffer which enables the WM subcomponents to communicate with LTM 5.  LTM as a “crystallised” system of long-‐term knowledge. We will not discuss this part of the model further. 3/21/12
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13. The phonological loop Component of the B-‐H model which temporarily stores speech or verbally encodable informaNon The phonological loop is composed to two subcomponents: -‐ A short-‐term store of limited capacity -‐ An ar-culatory rehearsal process which repeats (rehearses) informaNon to maintain it in memory InformaNon goes into this store if… •  It is from speech that we physically hear •  It is “read out” from a short-‐term memory trace -‐ For instance, sub-‐vocally rehearsing an item. This is essenNally re-‐
entering it in the loop again! •  You see visual informaNon but remember by “saying it to yourself” (digits, leEers, nameable objects) 3/21/12
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14. For which phenomena can the phonological loop account? 1. The phonological similarity effect •  People show poorer recall for a list of similar sounding items •  Has been suggested that these individual items may have few disNnguishing features and are easier to confuse 3/21/12
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2. The word length effect - Verbal memory span
decreases as participants
are asked to recall longer
words (shorter words are
easier)
- Suggested that this is
because each word takes
more time to rehearse in
the phonological loop and
to recall
- A robust and wellreplicated finding!
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15. The visuo-‐spa-al sketchpad This store is responsible for image-‐based informaNon, and is also subject to memory span limits. Appears to consist of two subsystems which work closely together to hold and manipulate informaNon •  Memory for objects and their features (what) •  Memory for spaNal locaNons (where) Note the similarity of this disEncEon to the organisaEon of the visual system! Special tasks have been devised to selecNvely study one aspect or the other, see textbook 3/21/12
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15. The visuo-‐spa-al sketchpad -‐ task One illustraNon of a span limit on the sketchpad is visual paêrn span (Della Sala et al. 1999) -‐ ParNcipants are shown matrices with some cells shaded in, required to recall them -‐ Matrices start small (2x2) and are increased in size unNl parNcipant’s recall span is reached 3/21/12
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16. A new addi-on: the episodic buffer The original B-‐H model struggled to explain interacNons between working and long-‐term memory. The episodic buffer suggested as addiNonal component to link memory subsystems with percepNon and LTM input/output •  A mulN-‐dimensional (mulN-‐modal) space •  Streams of informaNon from various modaliNes such as sound, imagery are bound into objects, scenes, and other meaningful units Binding is the process of linking individual features into objects •  Also can apply to creaNng a meaningful sentence out of words •  This module could explain the memory span finding that we can remember twice as many words in a sentence as we can individual, unrelated words. 3/21/12
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17. The central execu-ve: `Control Tower’ for memory Central ExecuEve is an aên-onal controller: aEenNon crucial for deeper processing of informaNon, and for binding different types of informaNon together. •  The execuNve selects which possible pieces of informaNon to manipulate (the “work” in working memory!) •  Switches between tasks (not necessarily a funcNon specific to the memory system) •  Is finite -‐ its funcNons and the informaNon it manipulates are limited by aên-on. Resources are finite, and processing has an associated cost. Many of these funcEons discussed more generally in the aFenEon unit and reappear in other cogniEve topics. The central execu2ve as a director of mental work is an important concept with far-‐reaching implica2ons outside of memory. 3/21/12
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18. Back to the big picture of the Baddeley-‐
Hitch model 1.  Phonological loop for speech or any informaNon that can be verbally encoded and rehearsed 2.  Visuo-‐spaEal sketchpad for image informaNon, objects and features, spaNal locaNons/relaNonships 3.  Central execuEve for selecNng and controlling informaNon flow 4.  Episodic buffer for addiNonal mulN-‐
dimensional storage and binding informaNon 5.  Long-‐term memory for prolonged storage of declaraNve and non-‐
declaraNve informaNon 3/21/12
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References Course materials Memory (Baddeley, Eysenck, & Anderson, 2009) Other references The magical number seven, plus or minus two (Miller, 1956) Working memory: looking backward and forward (Baddeley, 2003) An experimental invesNgaNon of memory span (Brener, 1940) Seven plus of minus two: A commentary on capacity limitaNons (Shiffrin & Nosofsky, 1994) Human memory: A proposed system and its control processes (Atkinson & Shiffrin, 1968) Working memory (Baddeley & Hitch, 1974) 3/21/12
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Types of memory and models of memory

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