STRUCTURAL ACCOUNTS OF MEMORY

Transcription

1 STRUCTURAL ACCOUNTS OF MEMORY Lecturer: Dr. Benjamin Amponsah, Dept. of Psychology, UG, Legon Contact Information: College of Education School of Continuing and Distance Education 2014/ /2017

2 SESSION OVERVIEW This section aims at helping you to appreciate human memory in terms of its structures of sensory memory, short term memory and long term memory. This viewpoint maintains that memory can be considered as a system of components that have both structural and process aspects. Structurally, memory seems to differ notably in their nature and organization. By process aspects we are referring to the cognitive operations that transferred and altered the memories stored in different locations Slide 2

3 Session Objectives At the end of the session, the student will be able to Understand the structures of memory including sensory memory, short-term memory and long-term memory. Describe the relationship that exist between the structures and their interdependence. Understand that cognitive operations are brought to bear on the information before it can be transferred or evacuated from one location to another. Slide 3

4 Session Outline The key topics to be covered in the session are as follows: Topic One: Structural Accounts of Memory Topic Two: Sensory Memory (Register) Topic Three: Short-term Memory Topic Four: Separation of STM and LTM Memories Topic Five: Long-term Memory Slide 4

5 Reading List Ashcraft, M. H. (2006). Cognition (4 th edn.), London: Pearson Education Int. Galotti, K. M. (2004). Cognitive Psychology: In and out of the laboratory (3 rd Edn.). Belmont, CA: Wadsworth. Hunt, R. R. & Ellis, H. C. (1999). Fundamentals of Cognitive Psychology (6 th edn.), New York: McGraw-Hill. Willingham, D, B. (2001). Cognition: The thinking animal. NJ: Prentice-Hall. Slide 5

6 Topic One STRUCTURAL ACCOUNTS OF MEMORY Slide 6

7 Structural Accounts of Memory The information processing viewpoint maintains that memory can be thought of as a system of interrelated components that have both structural and process aspects. By structural aspects we mean memories seem to differ markedly in their nature, duration and organization of information. For example, if we consider the duration of memory task, we realize that if you are distracted while trying to memorize something unfamiliar, the memory will certainly vanish, indicating that memory is fragile. Slide 7

8 Structural Accounts of Memory Information kept in memory therefore seems to differ in terms of the nature of the code, duration, capacity and so on. Other memories seem to be much more permanent, suggesting that memories are stored in different locations. We may hang on to memory stored permanently but memory has to go to a temporary location first. By process we are referring to cognitive operations that transferred and altered the memories stored in different locations. Slide 8

9 Information Processing Position The information processing paradigm is the most popular theory in the study of cognition. In the 1950s, Communication science and Computer science began to develop and became popular. Several researchers then began speculating that human thought process could be analyzed from similar perspective (Reed, 1997). Slide 9

10 Information Processing Position The influence of computerization is exerted at two levels; One is to provide a metaphorical language (figurative or symbolism that may not literally represent real things) and Second is a more specific use of the computer program as a theory of the mind. Similarity in storage function and Search process The storage function of the computer is also analogous to the process we normally think of as memory. The stored information can later be retrieved, used to solve a problem, and then expressed as output from the computer. Slide 10

11 Information Processing Position It is also striking to see the similarity in the search process and the problem-solving activities of the computer and human beings. Note: Using the computer as an analogy, however, is far from suggesting that the human brain works like a computer. The brain processes of perception, thinking, memory and language are much more complex than those of any existing computer. However, the computer model provides a general way of thinking about human cognitive functioning. Slide 11

12 Summary In summary the two important components of the information processing approach assume that: (a) mental process can best be understood by comparing it with the operations of a working computer. (b) mental process can be interpreted as information progressing through the system in a series of stages, one step at a time. Slide 12

13 What is Information? In cognitive psychology, information refers to any attended input, idea, image, fact, knowledge etc. Information represents things we see, hear, feel and so on. To process means to move toward some goal by going through a series of stages or sequence of acts or actions until the desired outcome is reached. These actions may produce a change or development. Slide 13

14 Basic Parts of Information Processing 1. The theory considers memory as a system of interrelated components. 2. Each component referred to as storage is capable of processing particular types of cognitive codes (representation of physical energy by the nervous system that is potentially capable of entering our awareness). 3. The information we receive from the environment (e.g., light waves) are precategorical (no meaning), which means that the physical energy has not been categorized. 4. Psychological processes must interact with the physical energy in order to add meaning to sensory experiences. Slide 14

15 Basic Parts of Information Processing The question is why is it difficult to identify an object when cues are based solely on visual description of that object? (a) The difficulty is due in part to the fact that visual properties do not exhaust the meaning of an object. (b) When we extract meaning from visual experience, we actually add more information to that experience. That is, the visual properties of an apple activate other knowledge of apples such as taste, smell, color and information such as fruit. Slide 15

16 Basic Parts of Information Processing 5. Finally, the information processing theory holds that cognitive codes can be transferred from one storage to another storage using controlled processes (effortful cognitive processes that require the allocation of attention to sustain them). A model of this representation showing the interrelated components called storages and the links are demonstrated in Figure 1.2. Slide 16

17 Basic Parts of Information Processing Figure 1-2 Atkinson and Shiffrin s (1964) Stages of Memory (also referred to as Modal Model Theory of Memory Slide 17

18 The Components The first of the storages is known as the sensory register. This is where the feature detection and pattern recognition processes rapidly produce a cognitive code that can be stored for a brief period. Slide 18

19 The Components The modal model theory shows three different storages that differ in their capacities, durations, operating characteristics (type of codes and mechanism of loss). This multi-store model became very popular within the emerging field of cognitive psychology. Because Atkinson and Shiffrin s model became standard approach, it is often called the modal model. The theory proposed that memory can be understood as a sequence of discrete steps, in which information is transferred from one storage area to another and this was consistent with the information processing position. Slide 19

20 The Components Sensory memory is assumed to possess a large-capacity storage system that records information from each of the senses with reasonable accuracy. The stored information is next transferred to other stores like the Short-term memory, where certain cognitive processes are brought to bear on the information. Slide 20

21 Summary Structures of the memory system The information processing position in terms of the assumptions made. Atkinson and Shiffrin s model, also referred to as the modal model or the stage model You have also become familiar with the terms (storages) sensory memory, short-term memory and long-term memory, which are of course interrelated in one model. Slide 21

22 Topic Two SENSORY MEMORY (REGISTER) Slide 22

23 The Sensory Storage The sensory store or sensory register is a memory system designed to store a record of the information received by the receptor cells. Receptor cells are the specialized sense organs of the ear, eye, nose, tongue and skin, which respond to physical energy from the environment. Firing the receptor cells begins the psychological processes of seeing, hearing, smelling, tasting and feeling. Once these receptor cells are activated, the record of this activation is preserved or stored in the sensory registers. The stored record is known as the sensory trace. Slide 23

24 Using the Information If we want to use the information in the sensory memory (the sensory trace), we must quickly encode it into a more durable form. Processing that information begins with attention, which selectively determines what will 'get through' for further examination and what will not. Attention allows us to focus on parts of the stimulus and thereby to recognize some of its features. Sensory memory allows us to take a 'snapshot' of our environment, and to store this information for a brief period. Only information that is transferred to another level of memory will be preserved for more than 1 or two seconds Slide 24

25 Using the Information Information processing thus begins with the activation of sensory receptors and this pattern of activity is stored in a memory system, the sensory register. Why do we need to store or maintain the sensory trace? Slide 25

26 Functions of the Sensory Register (a) The sensory register serves as a buffer or a holding bin for sensory information until the interpretative processes are free. The information is held until other cognitive processes are capable of interpreting or adding meaning (Hunt& Ellis, 1999). (b) This initial memory helps us to avoid losing present information while we are processing the one which just occurred. In other words, it helps us to avoid immediate decay of information (Hunt& Ellis, 1999). Slide 26

27 Characteristics of the Sensory Register There are certain important characteristics of the sensory register that enables it to serve its storage function optimally. (1) The information is stored in a veridical form. This means that the information stored should accurately reflect what happened at the sensory receptor. Slide 27

28 Characteristics of the Sensory Register (2) The sensory register needs to be relatively large. Large enough to store all the information impinging on the sensory receptor. Both characteristics are necessary because the sensory trace is precategorical. (3) The information remains on the sensory register for only a brief period of time. It has rapid decay time (brief trace life). The sensory register is also thought to be modality specific (that is, part of the storage is devoted to visual stimuli and part to auditory stimuli). Slide 28

29 Characteristics of the Sensory Register The contents of the sensory register must be cleared quickly to avoid superimposing information from two exposures. Therefore a conceivable means to avoid superimposition is a rapid decay time for the sensory register. Slide 29

30 Characteristics of the Sensory Register Experimental evidence supports each of the characteristics. Let us examine some of the evidence and their implications. Size and Duration of the Sensory Register A very important study by George Sperling (1960) illustrates well some of the important properties of visual (iconic) memory. We have sensory modalities of vision, hearing, touch, taste and smell they are presumed to have their own subsystem within sensory memory. Slide 30

31 Size and Duration of the Sensory Register Visual sensory memory - George Spelling Experiment Array of letters (letter matrix such as the matrix below) were presented very briefly (duration of 50 ms) [.05 of a second]), it was so brief that subjects could not rehearse verbally the letters in the display, and were followed by a blank white viewing field. Slide 31

32 A Twelve Letter Matrix and a Tachistoscope A Twelve Letter Matrix Tachistoscope Slide 32

33 Size and Duration of the Sensory Register Sperling s Research tells us 4 important things about Visual Sensory Memory: (1) More can be seen in a single glance than can be remembered. The capacity of the sensory memory appears to be very large and that a complete (or nearly complete) and brief memory record of a complex stimulus can be provided in a brief glance. (2) The memory record appears to be in the form of a literal (visual) copy (veridical) of the eliciting stimulus, since its duration depends on viewing conditions and there is not time for the letters to be named individually and then rehearsed. Slide 33

34 Size and Duration of the Sensory Register (3) The duration of iconic memory is very short, effective approximately 300 milliseconds. (4) The fading away of the icon seems to reflect a decay process. Forgetting from sensory memory seems to be caused by decay. There is little reason to believe decay is caused by interference of some sort. According to the theory, such traces gain access to more durable representations when they are acted upon by control processes such as attention and rehearsal. Slide 34

35 Topic Three SHORT-TERM MEMORY Slide 35

36 Short-term Memory Information processing theorists believe that cognitive codes are next transferred from the sensory register to a component called the Short-term memory. Cognitive codes stored in short-term memory can be transferred to a long-term storage whose capacity like the sensory register, is extremely large. The control process that permits the transfer of coded material between short-term memory and long-term storage is referred to as Rehearsal. Slide 36

37 Short-term Memory The term rehearsal has so many meanings in cognitive psychology, but for our purpose we will restrict its usage to two procedures: (1) Rehearsal refers to procedures that maintain the vitality of the code or information in short-term memory. As long as the short-term code is occasionally refreshed by rehearsal, it can reside there for long periods (rote or maintenance rehearsal). Slide 37

38 Short-term Memory (2) Rehearsal also refers to operations that build up a corresponding code of the short-term material in long-term storage (elaborative rehearsal). That is, rehearsal operates by duplicating a representation of the short-term material in long-term storage Maintenance rehearsal aims at keeping the code active and Elaborative rehearsal aims at transferring the code from the shortterm to the long-term memory. Another important control process in the short-term memory is coding, which involves attaching appropriate information from long-term memory to the short-term information. Slide 38

39 Short-term Memory We can now define STM as : A conceptual system which not only stores information, but also serves as a work space for rehearsing, coding, retrieving and decision making. Slide 39

40 Short-term Memory Klatzky (1980) uses the workbench analogy to explain the short-term memory phenomenon. That is, items from other stores may be transferred to the bench to be worked on and changed to different shapes or even transformed entirely. Benches have limited space, which means it can contain only a few items at the same time. Slide 40

41 Sensory and STM DIFFERENCES - SENSORY MEMORY AND STM: Short-term storage differs from the sensory memory in several ways. Some of these are:. The capacity of the short-term memory is assumed to be quite limited. The sensory register has large capacity and it is unlimited. The information in the short-term memory is organized in a cognitive code that is Acoustic /AVL. Information in the sensory register is veridical and precategorical. Slide 41

42 Sensory and STM Similarity: The short-term memory and the sensory memory are similar in one aspect. In both cases, material that is not attended to, elaborated and transferred certainly decays. Slide 42

43 Characteristics of the Short-term Memory Three basic characteristics have been proposed to distinguish short-term memory and the long-term memory. Trace life (duration) Storage Capacity Nature of the code 1. Trace life (Duration of the Short-term Memory) As information moves from sensory memory to short-term memory, the trace life increases somewhat, although it is still brief when compared to the duration of the long-term memory. Slide 43

44 Characteristics of the Short-term Memory There have been classic experiments to demonstrate the short-term trace of the short-term memory. Two experiments reported simultaneously by Brown (1958) in England and Peterson (1959) in the US are used to demonstrate the trace life of the short-term memory. The experimental procedure has come to be known as the Brown-Peterson s paradigm (Hunt & Ellis, 1999). Slide 44

45 Characteristics of the Short-term Memory 2. Capacity of Short-term Memory George Miller (1956) a prominent psychologist conducted a series of studies concerning immediate memory performance. Miller noticed that most people remembered between five and nine items (7±2 items), which suggested that short-term storage has quite limited capacity. The limitation of short-term storage capacity is additional evidence calling for separate memory systems (short-term and long-term memory stores). Slide 45

46 Characteristics of the Short-term Memory 3. Nature of the Code in Short-term Store Another distinction between short-term memory and the other stores is the memory code of each system. Information stored in long-term memory is assumed to be based on semantic code whereas short-term is acoustically or phonetically coded. In other words, information stored in long-term memory is in terms of its meaning whereas sound patterns are remembered in the short-term memory. Slide 46

47 Topic Four SEPERATION OF SHORT-TERM AND LONG-TERM MEMORY Slide 47

48 Separation of Short-term and Long-term Memories Separation of Short-term and Long-term Memories Short-term memory has a brief trace, small capacity and is acoustically coded, whereas long-term memory is assumed to be permanent, have large capacity and semantically coded (based on meaning). Serial Position effect When a subject s memory is tested in a free-recall situation, initial and final items are more likely to be recalled than items presented in the middle of the list. Slide 48

49 Separation of Short-term and Long-term Memories That is, early items are recalled well and so are the last items, but the middle items are remembered poorly, which results in a U-shaped function. Slide 49

50 Separation of Short-term and Long-term Memories Demonstration of Serial Position Effect Slide 50

51 Separation of STM and LTM Neuropsychological Evidence Neuropsychological evidence Studies of amnesic patients provide another source of indirect evidence for the distinction between STM and LTMs. Alzheimer s disease produce a memory impairment known as anterograde amnesia (after inability to remember events that occur after injury - accident or disease). What has emerged is that we have two distinct memory systems which obey different principles and produce different retention. Slide 51

52 Topic Five LONG-TERM MEMORY Slide 52

53 Long-term Memory The long-term memory or storage is the ultimate repository of our knowledge or experience from day one. The LTM is a concept which represents the vast store of knowledge we have about the world, ranging from everyday events such as how to use a knife and fork to more esoteric information such as axioms of geometry. Two lines of evidence have traditionally being used to support the idea of a long-term storage. Slide 53

54 Long-term Memory The first concerns the nature of the memory code which changes as a function of its time in the memory system. The second evidence comes from neuropsychological literature (a sub-discipline in physiology and psychology that focuses on the relationship between neurological processes and behaviour) which points to a distinction between STM and LTMs. Slide 54

55 Structure of the Long-term Memory The long-term memory is a well organized store of events and as such it is well structured and organized. This is the structure. Schematic representation of contents of long-term memory Slide 55

56 PROCEDURAL MEMORY This is the part of the long term memory made up of conditioned responses. Usually, it is expressed as skill (requiring training and experience) or disposition (inclination or certain types of automatic reactions). It s about knowledge of how to perform various tasks e.g., lacing a shoe, riding, driving, typing, using fork and knife etc. Slide 56

57 Declarative Memory This constitutes the part of long-term memory containing factual information. It is about knowledge about which a person can make a declaration. These include knowledge, facts, information, ideas, or anything that can be recalled and described in words, pictures or symbols. Endel Tulving (1983) has proposed a distinction between two types of permanent LTMs (Semantic and Episodic Memories). Slide 57

58 Declarative Memory Episodic memories are autobiographical, personal and sensitive to the effects of context. These are memories organized by time and place of occurrence (autobiographical reference). Slide 58

59 Semantic Memory Semantic Memory This section of the LTM refers to encyclopaedic knowledge of the world and language. In other words, it s general knowledge that is not specifically timetagged. These are memory of words, concepts, rules and language. It s simply a mental encyclopaedia or thesaurus. Slide 59

60 DISTINCTION BETWEEN EPISODIC AND SEMANTIC MEMORY CHARACTERISTIC EPISODIC MEMORY SEMANTIC MEMORY 1. Source of information Sensory experiences things we see, hear etc 2. Units of information Episodes and events that are context based Comprehension things understood Concepts, ideas, and facts 3. Organization Time-tagged or related Conceptual 4. Emotional content of the memory More important Less important 5. Likelihood of forgetting Great, imagine things you have to recall based on time e.g., 1.00pm, 2.00pm etc. Small 6. Time required to remember info. Relatively long time Relatively short time 7. How it s tested in the laboratory Recall of particular episodes General knowledge 8. Interference Highly susceptible Less susceptible More useful, based on 9. General usefulness Less useful meaning, comprehension

61 Sample Questions Why do you think that the nature of the cognitive code in the short-term memory is acoustic? Discuss the various meaning of rehearsal? Discuss evidence from neuropsychological research and the serial position effect as further evidenc.e of the separation between STM and LTM. Outline the structure of the LTM Slide 61

62 References Atkinson, R. C. & Shiffrin, R. M. (1964). Human memory: A proposed system and its control processes. In K. W. Spence & J. T. Spence (Eds.), Advances in the psychology of learning and motivation: Research and theory (vol. 2). New York: Academic Press. Best, J. B. (1995). Cognitive Psychology (4 th Edn.). MN. West Publishing Company. Hunt, R. R. & Ellis, H. C. (1999). Fundamentals of Cognitive Psychology (6 th edn.), New York: McGraw-Hill. Slide 62

63 References Klatzky, R. L. (1980). Human Memory: Structures and processes (2 nd ed.). San Francisco: Freeman. Reed, E. (1997). The cognitive revolution from an ecological point of view. In D. M. Johnson & C. E. Erneling (Eds.), The future of the cognitive revolution (pp ). New York: Oxford Univ. Press. Sperling, G. (1960). The information available in brief visual presentations. Psychological Monographs, 74, Slide 63