Inf1: Intro to Cognive Science Types of memory and models of memory Alyssa Alcorn, Helen Pain and Henry Thompson March 21, 2012 Intro to Cognitive Science 1 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 Intro to Cognitive Science 2 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-spaal informaon, the disNncNon of short vs. long-term applies to other types of sNmuli as well. 3/21/12 Intro to Cognitive Science 3 3. Memory span and magic numbers Amount of informaon 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 (dramacally!) “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 Intro to Cognitive Science 4 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 illustrang 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 Intro to Cognitive Science 5 4. Maybe not a magic number? Memory span results were widely confirmed and replicated for many years, but (relavely) 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 variaon in the retenNon properNes for different types of informaon See Shiffrin & Nosofsky 1994 for a review and further references. 3/21/12 Intro to Cognitive Science 6 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 informaon - easier to remember one year, 1918, than four numbers 1, 9, 1, 8 - naturally “recode” informaon 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 Intro to Cognitive Science 7 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 relaonship is more complex. These are NOT interchangeable terms. • Working memory (abbreviated to WM) is the part of memory conceived as a “mental workspace” where informaon is temporarily maintained and manipulated. • Short-term memory as discussed earlier in this lecture is more specifically concerned with storage, maintaining small amounts of informaon (e.g. “keeping them in mind” but not manipulang them or processing them more deeply) 3/21/12 Intro to Cognitive Science 8 STM v. WM contd. As you will see in this lecture, the disncon 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 Intro to Cognitive Science 9 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 Intro to Cognitive Science 10 8. The Modal Model of memory Early memory model (Atkinson & Shiffrin, 1968) proposes the following general sequence of processing steps: 1. Informaon enters from the environment 2. Brief processing in sensory systems 3. Informaon goes to a short-term store (STS) – Passes informaon in and out of LTM – Workspace to perform operaons, select/ rehearse informaon – Items would be learned if held in this store 4. Informaon is output OR goes into long-term store (LTS) 3/21/12 Intro to Cognitive Science 11 8. The Modal Model of memory From Baddeley textbook 3/21/12 Intro to Cognitive Science 12 9. Difficul-es with the Modal Model While a simulaon 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 informaon into and out of the LTS (encoding and retrieval) • If STS is a “workspace” for manipulang informaon, a STS deficit would impair a person’s ability to do complex cogniNve tasks (e.g. reasoning) 3/21/12 Intro to Cognitive Science 13 9. Difficul-es with the Modal Model, contd. However, empirical evidence contradicted both predicons (these are just two examples) • A case in Shallice & Warrington 1970 reported a paent with severe deficits characterisNcs of the STS, but who also had an unimpaired LTS. • Other paents 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 Intro to Cognitive Science 14 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 manipulaon of informaon is necessary for many complex tasks, such as adding digits in one’s head. 3/21/12 Intro to Cognitive Science 15 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 funconal role as a system that underpins complex cogniEve acviEes, 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 stac photo album or filing system. 3/21/12 Intro to Cognitive Science 16 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 informaon, unlike earlier Modal model. More typically called the mulEcomponent theory The components connect to one another as shown. - Arrows indicate in which direcNons informaon can move. 3/21/12 Intro to Cognitive Science 17 12. The B-H model components The components are : 1. A phonological loop for processing and encoding verbal and auditory informaon 2. The visuo-spaEal sketchpad for processing/encoding visual and spaal informaon 3. A central execuEve as an “aenNonal controller” to direct the “work” performed by working memory.