Working Memory Chapter 4 1 Working Memory Some memories are very fragile and go into oblivion very quickly. Working memory is one such memory. 1. Try this. Do this mentally. Write your answers on paper. a. 7 X 9 = 63 b. 74 X 9 = 666 c. 74 X 96 = 7104 2 Working Memory (WM) 1. We know attention is limited. So information that gets to memory is also limited. Thus capacity of working memory is limited. 2. Working memory is brief, immediate memory we use for current information. A portion of working memory coordinates ongoing mental activities. 3. Working memory has been known as short-term memory, and is contrasted from long-term. Some investigators believe the two are the same (Nairne, 2002). 3 1 Classic Research on Working Memory (Short-term Memory) 4 Short-term Memory In the 19th century, Sir George Hamilton discovered that he could accurately store about 7 items (marbles) in memory if he glanced at the items quickly. If the items were more than 7 his accuracy decreased. Sir George Hamilton 5 Short-term Memory 1. Miller (1956) wrote, “The magical number seven plus or minus two: some limits on our capacity for processing information”. 2. Miller suggested that the capacity of our short-term memory was small. We could store about 5-9 items in it. 3. He also showed that items could be “chunked”, which would increase our memory capacity. George Miller 6 2 Try This ! C T A I I L T C S F R O R E C A L L ! F R A C T O L I S T I C R E C A L L ! 7 Another Example 870-230-5339 (10 items) 870 + 230 + 5 3 3 9 (1) (1) (4) 2 chunks + 4 items (6 items) Capacity of short-term memory may be increased by a process called “chunking”. 8 Miller’s Memory Miller thus conceived of short-term memory as a passive store capable of holding 7±2 items or chunks. 7 5 870 apple 1876 P water 3 Z Working Memory 9 3 Short-term Memory: Duration Brown (1958) Peterson and Peterson (1959) used blocking of rehearsal to measure the duration of short-term memory. 10 Short-term Memory: Duration These experiments suggested that duration of information in short-term memory stays for about 18 seconds and then decays, unless rehearsed. 100 90 80 70 60 50 40 30 20 Percent Correct Recall Correct Percent 10 0 0 3 6 9 12 15 18 Time Delay (Seconds) 11 Recency Effect 1. Short-term memory (and long-term memory) have been studied through serial position effect procedures, which generate a U-shaped curve. 2. When a list of items are recalled, items at the beginning of the list and at the end of list are recalled more than the items in the middle. This is called the serial position effect. 3. Recall of beginning items refers to primacy effect and the items recalled at the end of the list refer to recency effect. 12 4 Recency Effect 12 dizzy 13 car 14 apple 15 jet 16 groom 17 pair Primacy Recency Effect Effect 18 blue 19 pride 20 water Short-term Memory List 4. Recency effect can also determine the capacity of short-term memory. 13 Model of Memory 1. Based on experiments like serial position effect Atkins and Shiffrin (1968) proposed two separate stores for short-term (recency effect) and long- term (primacy effect) memories. 14 Model of Memory 2. Atkins and Shiffrin (1968) also suggested that control processes like rehearsal could improve short-term memory. 3. With recent advancements by Alan Baddeley our way of looking at short-term memory has changed. In fact the name short-term memory has changed to working memory. 15 5 Factors Affecting Working Memory 1. Capacity of working memory may be affected by the length of the items on the list. If each item on the list was short (single syllable) it would take less time to pronounce it. 2. Memory capacity improved with shorter pronunciation time than when it was longer. Short Pronunciation Long Pronunciation Burma Switzerland China Nicaragua Greece Afghanistan Cuba Philippines 16 Pronunciation Time 3. The most through study on pronunciation time on the capacity of shot-term memory was carried out by Naveh-Benjamin and Ayres (1986). 4. The investigators took numbers in four languages and looked at memory spans. 5. Since number in English and Spanish were shorter than Hebrew and Arabic. Capacity of memory spans were greater in former than latter languages. 17 Syllable Length No. English Spanish Hebrew Arabic 1 One Uno Eh'ad Wa’hid 2 Two Duo Shnyim Ith’n’an 3 Three Tres Shlosha Tha’la’tha 4 Four Cuatro Arba'a arba’a 5 Five Cinco H'amisha Kham’sa 6 Six Seis Shisha Sit’ta 7 Seven Siete Shiv'a sab’a 8 Eight Ocho Shmona Tha’ma’niya 9 Nine Nueve Tish'a tis’a 10 Ten Diez Assara ‘ashra Syl 1.0 1.6 1.9 2.4 18 6 Memory Span Results clearly show that as the pronunciation time increases the memory span decreases. 8.0 7.0 6.0 Memory Span 5.0 English Spanish Hebrew Arabic 1.0 1.6 1.9 2.4 Mean Syllable per Digit 19 Proactive Interference 1. Meaningfulness of words can have important affect on capacity of working memory. 2. Wickens and colleagues (1976) used proactive interference and release from it to show how capacity of memory can increase. 3. Proactive interference involves having trouble learning new material because older material interferes, especially if the material to be learnt is the same or similar. 20 Proactive Interference: Release 4. However, there can be release from proactive interference when new material is different from older material. 5. Wickens and colleagues (1976) used 5 semantic categories, fruits, vegetables, flowers, meats, and occupations as new material to be learnt when the original category was fruits. 6. Results showed a consistent release from proactive interference as the categories became more and more dissimilar. 21 7 Semantic Similarity 100 90 80 70 Occupations 60 Meats 50 Flowers 40 Vegetable Percent Correct Percent 30 20 Fruit 10 0 1 2 3 4 Trial 22 Working Memory Approach 23 Non-unitary Nature of Working Memory 1. What caused Baddeley to suggest that working memory is not unitary? 2. Baddeley and Hitch (1974) gave participants random numbers 0-8 digits long to rehearse in order, and also gave them spatial reasoning task to perform. Showed BA, and then a statement A follows B. Answer yes. 3. Simultaneously doing reasoning task did not increase errors on recall of random numbers. Suggesting that working memory had multiple parts, with overall larger capacity as envisioned by Miller. 24 8 Model of Working Memory Baddeley (2006) final division of working memory consisted of the following components. Working Long-term Memory Phonological PhonologicalMemory Loop Loop Central Episodic Episodic Executive Buffer Buffer Visuospatial Visuospatial Sketchpad Sketchpad 25 Phonological Loop 1. Many studies proposed that phonological loop was acoustical in nature. 2. And involved rehearsing verbal material in this acoustical form. 3. If verbal material is acoustical in form then many errors in working memory can be based on acoustical confusions. Working Memory Phonological Loop 26 Rehearsal Acoustical Confusions 4. Wickelgren (1965) showed that acoustical confusions lead to errors when similar sounding letters and numbers were recalled. Lists Errors Recall 4 N F 9 G 4 B 3 0 R 2 P, E, V, D, 3 P 5 A 7 6 E 5 6 8 C Z 8 6 Y 2 4 K L Y 3 K N 2 D C, E, V, D, B C N Q 5 H 1 N T 1 C 5 7 T 27 9 Acoustical Confusions 5. Kintch and Buschke (1969) showed that homonyms cause similar acoustic confusions. When asked to recall the word after the word so (sounds like sew) the participants erred in recalling tax. Recall Error Recall Tacks So Sew Buy Buy Owe Tied Sew So Tax Tax 28 By Division of Phonological Loop Gathercole & Baddeley (1993) have recently suggested that phonological loop could be further subdivided into two parts. Working Phonological Memory Store Sub-vocal Rehearsal Process Phonological Loop 29 Biology of Phonological Loop Recent studies have suggested that phonological loop resides in left hemisphere. The phonological store resides in parietal cortex and sub-vocal rehearsal process in the frontal cortex. Parietal Frontal Cortex Cortex Left Hemisphere 30 10 Visuospatial Sketchpad 1. A division of working memory that generates and stores visual and spatial information. 2. Visuospatial sketchpad stores information about a visual scene and lets us navigate through it. 3. The sketchpad stores a coherent picture of objects in the scene and their relative position in it. Working Memory Visuospatial Sketchpad 31 Visuospatial Sketchpad 4. It stores visual information processed by verbal stimuli. Visualization or imagining related stories. 5. Visuospatial sketchpad also has limited capacity, like the phonological loop. To much information in the store makes it difficult to accurately recover the information. 32 Visuospatial Sketchpad: Research 1. Perceptual processes and processes that require imagination cannot be carried simultaneously (Baddeley, 1999; 2006). 2. There is not a lot of research carried out on the visuospatial sketchpad: a. No standard visual stimuli like letter or words for verbal tests. b. People tend to respond to visual stimuli by giving them names. 33 11 Visuospatial Sketchpad: Uses 1. The sketchpad is useful for people in engineering and architectural disciplines. 2. Sketchpad retains images thus we can interact with environment using our imagination.