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Short-term working memory • James, Galton, and others have proposed a memory system that keeps in consciousness a small number of ideas • William James referred to this system as primary memory • the primary memory is probably more closely related to working memory than to STM Short-term working memory • Short-term memory capacity is measured using a memory-span procedure • Memory span procedure: participant presented a sequence of items, and is required to repeat them back; start with one item, increasing the number of items by 1 until the participant makes mistakes Short-term working memory • the point at which the participant is able to recall all items correctly 50% of the time is designated as her/his memory span • factors affecting memory span – auditory presentation leads to larger memory span estimates than visual presentation – rhythmic presentation is better than non-rhythmic presentation Short-term memory – The next slide contains a series of digits. The digits are presented in pairs. Read the pairs of digits rhythmically aloud. Pause between each pair. For example, suppose the digits were 24 89 17 14 29 12 3 – After you have read the pairs aloud, I want you to write down as many digits as you can remember. Any questions? Read aloud these digits • 41 64 00 40 11 49 2 Short-term memory – The next slide contains a series of digits. The digits are presented in groups. Read groups of digits aloud. Pause between each group. For example, suppose the digits were 248 917 142 9123 – After you have read the list aloud, I want you to write down as many digits as you can remember. Any questions? Read aloud these digits • 416 400 401 1492 Short-term working memory • factors affecting memory span (cont’d) – recoding or chunking information; George Miller showed in his classic paper (1956) that memory span is determined by the number of ‘chunks’ or integrated items to be recalled, not the number of items presented – Inducing rapid forgetting • Brown-Peterson paradigm – Brown (1958) and Peterson & Peterson (1959) showed that very rapid forgetting is possible – paradigm study: present a small number of items followed by a number such as 632. Participant is required to count backward by threes until given a recall signal. Then he/she attempts to recall studied items Inducing rapid forgetting Percent correct recall Peterson & Peterson (1958) Recall of three consonants 100 80 60 40 20 0 0 3 6 9 12 Retention interval (sec) 15 18 Inducing rapid forgetting Note: Murdock (1961) showed that performance is about the same for 3 consonants as it is for 3 words, illustrating the importance of chunking – why is information forgotten in the BrownPeterson paradigm? Inducing rapid forgetting • why is information forgotten in the BrownPeterson paradigm? Two possibilities – trace decay: automatic fading of memory – interference: memory is disrupted by other memory traces Inducing rapid forgetting • Two types of interference – proactive interference: effects of prior items on recall of subsequent items – retroactive interference: effects of subsequent items on recall of previous items Inducing rapid forgetting • why is information forgotten in the BrownPeterson paradigm? – Petersons argued that it must be trace decay; it couldn’t be retroactive interference because numbers are very different from consonants – Keppel & Underwood (1962) showed that proactive interference seemed to be responsible because if performance on the first trial only is examined there is little decline in performance over the retention interval Inducing rapid forgetting • Further evidence for the importance of proactive interference (PI) – release from PI – numerous studies have established that if you present several lists of items using a BrownPeterson procedure (Study: present list of 3 items; count backwards by 3s for 15 sec, then attempt recall of the studied items. Results show that performance declines across lists Inducing rapid forgetting • Results show that performance declines across lists (build up of PI) • If categories studied are changed, then recall of the changed category increases (release from PI) One or two memory systems • Are STM and LTM distinct? – One approach to investigating this question involves determining whether certain tasks have separable components • One task is free recall Percentage correct recall Free Recall performance (Craik, 1970) 100 80 60 Immediate Delayed 40 20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Serial position Interpretation of free recall study Primacy and intermediate components of the serial position curve are lower in the delayed compared to immediate condition Key result: recency portion of the curve is differentially lower in the delayed condition interpretation: delayed condition has a stronger influence on recency portion of curve because recency reflects STM Neuropsychological Evidence for separation of STM and LTM Data from amnesics support distinction between STM and LTM Evidence: amnesics have normal digit span, which is mediated by STM, but are impaired in their ability to acquire and retain LTM memories Neuropsychological Evidence for separation of STM and LTM Free recall data in amnesics also supports this distinction. predict performance of amnesics (Baddeley & Warrington, 1970) In immediate free recall, how should amnesics perform on the recency portion of the curve? What about the primacy portion of the curve? Short-term working memory • Atkinson-Shiffrin model of memory (1968) – distinguishes between two types of memory: short-term and long-term memory – short-term memory (STM): a temporary storage system capable of holding a small amount of information (e.g., telephone number) – information in STM is forgotten quickly unless it is rehearsed or transferred into LTM – Long-term memory (LTM): a permanent memory store with no capacity limitations Atkinson-Shiffrin model of memory Rehearsal Incoming information Short-term memory Long-term memory Transfer Information displaced Problems with modal model • Atkinson-Shiffrin model assumes that STM plays a critical role in the transfer of information into LTM – Specifically, this model suggests that the capacity of the STM should determine the probability that an item enters LTM and – The amount of exposure in STM should affect the likelihood that an item enters into LTM Problems with modal model • Both these implications are incorrect – several studies have shown that under some conditions the number of times material is rehearsed is a poor predictor that it will be recalled subsequently (shallow rehearsal) Problems with modal model – Shallice and Warrington (1970) and others have established that at least some people with poor memory span (this suggests that STM is damaged) have normal long-term memory KF had impaired memory span (KF memory span WAIS score = 2, Mean = 10, Standard deviation = 3 KF’s long-term memory performance was unimpaired Summary • Evidence supporting STM vs LTM distinction – tasks such as free recall seem to have both STM and LTM components – Neuropsychological evidence suggests that both components can be selectively damaged amnesics have damaged LTM component, but intact STM component KF (and others) have damaged STM but intact LTM Summary • However, the modal model (Atkinson-Shiffrin) does have problems accounting for – the finding that patients with STM deficits appear to have intact LTM – maintaining an item in STM does not ensure its transfer to LTM Working memory model of Baddeley • A different conceptualization of STM – Baddeley hypothesized STS is important because it acts as a working memory, a system that is important for holding and manipulating information – Hypothesized working memory needed for a broad range of cognitive tasks Working memory model of Baddeley • Experimental paradigm (dual task paradigm) – primary task: grammatical reasoning Determine whether sentences are true/false e.g., A follows B -- BA (true) e.g., B is not preceded by A - AB (false) – secondary task: concurrent digit task: remember number sequences ranging in length from 0 to 8 Baddeley (1986) cont’d • Results – reasoning time increased with concurrent digit load. However, performance remained high, and errors remained low (about 4% and did not vary with digit load); see figure – thus, overall performance remains quite good, even when the overall digit load is 8 (memory span capacity) Baddeley (1986) Speed of reasoning by concurrent digit load Reasoning time (seconds) 3.1 2.9 2.7 Reasoning time 2.5 2.3 2.1 0 2 4 6 Concurrent digit load 8 Baddeley (1986) cont’d • Conclusions – Hypothesized two systems are involved in this task One system stores digits (phonological loop) A second system manipulates information in the reasoning task (central executive) See Baddeley’s working memory model Baddeley’s working memory model Visuo-spatial sketchpad Phonological loop Central Executive Working memory model of Baddeley – Basic model of working memory consists of a controlling attentional system (called the central executive) and two slave systems, an articulatory or phonological loop system and a visuo-spatial sketch pad Working memory • Phonological loop characteristics – consists of a phonological store (codes speechbased information), and maintains information for about 2 seconds – articulatory control process that refreshes items in store by means of subvocal rehearsal Working memory • Phonological loop – appears to play an important role in reading poor readers tend to have poor short-term memory span – also appears to play a role in the comprehension of language and in the acquisition of vocabulary Visuo-spatial sketchpad • Information can enter the sketchpad visually or through the generation of a visual image • access to this store by visual information is obligatory • the information in this store may be visual or spatial or both Central Executive • The central executive plays an important role in controlling attention. Central Executive • Vigilance – recall vigilance refers to sustained attention Parasuraman (1979) showed that vigilance performance decreases if the vigilance task has a short-term memory component involving storage and manipulation of information. Central Executive • Vigilance – Experiment Condition 1. discriminate between successive tones of various volumes (requires memory) Condition 2. discriminate between simultaneous tones of various volumes (no memory required) Performance declined in condition 1 but not condition 2 Central Executive • Vigilance Conclusion Performance declines over time if task requires working memory Central Executive • Effects of dividing attention on declarative memory performance – Studies showed that performing a concurrent task during the encoding phase of a declarative memory task (e.g., a list of words), reduced recall of studied words compared to encoding words a full attention – Dividing attention during recall of the studied words had a small effect on performance compared to recall at full attention Central Executive • Effects of dividing attention on declarative memory performance – Conclusion. Encoding words into declarative memory requires working memory. Retrieving words from declarative memory does not appear to require working memory (Baddeley, Lewis, Eldridge, & Thomson, 1984) Central Executive • Effects of dividing attention on procedural memory performance – Roy & Park (2016) investigated the effects of dividing attention on declarative and procedural aspects of novel tool use. – Participants trained to use a set of novel tools under full and divided attention Central Executive • Effects of dividing attention on procedural memory performance Central Executive • Effects of dividing attention on procedural memory performance – Results showed that dividing attention did not interfere with motor skill learning, a type of procedural memory – Conclusion. Encoding skilled actions into memory does not appear to require working memory Episodic buffer of working memory (Baddeley’s new model) • Overview – recently Baddeley updated the 3-component model of working memory – It proposes a 4th component, an episodic buffer It has limited capacity Stores information in a multimodal code Binds information from subsidiary perceptual systems and LTM into episodic memory Information is consciously retrieved Episodic buffer of working memory (Baddeley’s new model) • Background – 3 component model of working memory consists of central executive and two slave systems, the phonological loop and the visuo-spatial sketchpad – Central executive is an attention controller – Phonological loop stores speech-based info – Visuospatial sketchpad stores visual info Episodic buffer of working memory (Baddeley’s new model) • Problems with 3-component model of WM – Articulatory suppression Saying ‘the’ repetitively (occupying the phonological loop) does not have a devastating effect on recall of visually presented numbers Recall drops from 7 to 5 digits One might expect recall to drop dramatically because Phonological loop is occupied and VSS is not very good at storing this type of information Episodic buffer of working memory (Baddeley’s new model) • Problems with 3-component model of WM – Prose recall of a patient (PV) with word-span of 1 word is 5 words. This is less than the span of 15 words, but much more than 1 words Episodic buffer of working memory • Binding problem – Information that is processed independently by separate cognitive processes must be bound together because our experience of the world (and our memory of it as well) is coherent – People can also retrieve information about an episode when give part of an episode (e.g., given a spatial cue, state what object was stored there) – Episodic buffer is one way in which the binding problem can be solved 4-component model of WM (see Fig.1) Central Exec visspat Episodic Buff Episodic LTM Phon. Properties of Model • See previous notes for description of – Central Executive Function – Phonological Loop – Visual spatial sketchpad Properties of Model • Episodic buffer – Integrates information across modalities and from different sources (binds information) – Integrates information across time (binds information) – Has limited capacity – Manipulates information – Is consciously accessible from Central Executive A model of the Central Executive Supervisory Attentional System SAS • Norman and Shallice developed a model of the control of action called the Supervisory Attentional System – this model was developed by considering our knowledge of action slips and frontal lobe function A model of the Central Executive Supervisory Attentional System SAS • Action slips – probably all of us have had the experience of performing some unintended action e.g., driving home from York in your car and forgetting to make a detour to pick up your clothes from the dry cleaners e.g., William James… going upstairs and ending up in bed Reason (1979) showed that actions slips tend to occur when you are pre-occupied with some other thought A model of the Central Executive Supervisory Attentional System SAS • Action slips are actions that are inappropriate for the goals of the participant. However, the actions themselves are meaningful, and reasonably well performed – my driving is safe, I obey traffic rules etc. • This suggests that some actions, once they are initiated, can be accurately performed with little conscious attention being paid to them A model of the Central Executive Supervisory Attentional System SAS – Other actions and other types of behaviour seem to require a central system and performance declines if such a system is not in place research with damaged frontal lobe patients and monkeys suggests that performance is impaired if it requires coordination of different elements of a complex activity focused attention focusing on the whole of a task working on new situations A model of the Central Executive Supervisory Attentional System SAS – It is well established that patients with frontal lobe damage may have relatively intact performance on IQ tests – Luria (1966) proposed that the frontal lobes are involved in programming, regulation, and verification of activity A model of the Central Executive Supervisory Attentional System SAS – Sample problem given to pt with frontal damage There were 18 books on two shelves, and there were twice as many books on one shelf than on the other. How many books were on each shelf? Pt. Response Step 1. 18/2 = 9 (Clause 1) Step 2. 18 x 2 = 36 (Clause 2) A model of the Central Executive Supervisory Attentional System SAS – For problems such as these Shallice, Norman, and others have proposed that a central executive is needed – their model is presented in the next slide Supervisory Attentional System Perceptual Structures Trigger Data Base Effector System Contention Scheduling SAS system • According to this system routine actions run off relatively automatically – perceptual information comes into the system and it makes contact with stored information and that information triggers certain responses. These responses eventually result in actions that are produced by the effector system – e.g., walking on a country road SAS system • At any given moment this model postulates that our behaviour is controlled by schemata, that control lower-level programs – for example the schema that controls our driving requires visual spatial and motor control systems, and may call particular component schema in well-defined circumstances (e.g., if light turns orange, and you are well away from the intersection, start braking) SAS system – schemata are assumed to be activated by triggering inputs, and to be selected if the level of activation exceeds a threshold – they also tend to be mutually inhibitory – once a schema is selected, the component schema associated with a given schema become activated (e.g., component schema for braking, turning on lights, windshields etc.) – the process of routine selection between alternative actions is called contention scheduling SAS system – the process of routine selection between alternative actions is called contention scheduling; see Figure e.g., light is orange and you are close to intersection, do you brake, accelerate, or maintain speed and continue through intersection SAS system – in addition, this model assumes that there is an additional system, the supervisory attentional system this system has access to the environment and to the organism’s intentions it does not directly control behavior, but instead modulates the lower level contention-scheduling system by activating or inhibiting particular schemata SAS system – the supervisory attentional system is involved in initiating willed actions, and in working in situations in which routine actions are not satisfactory--e.g., dealing with novelty, overcoming temptation, etc.