Chapter 6 - Memory Unit 3 – Area of Study 2: Memory Pages 286-360
Study Design Content • mechanism of memory formation: – role of the neuron in memory formation informed by the work of E. Richard Kandel – roles of the hippocampus and temporal lobe – consolidation theory – memory decline over the lifespan – amnesia resulting from brain trauma and neurodegenerative diseases including dementia and Alzheimer’s disease • comparison of models for explaining human memory: – Atkinson-Shiffrin’s multi-store model of memory including maintenance and elaborative rehearsal, serial position effect and chunking – Alan Baddeley and Graham Hitch’s model of working memory: central executive, phonological loop, visuo-spatial sketchpad, episodic buffer – levels of processing as informed by Fergus Craik and Robert Lockhart – organisation of long-term memory including declarative and episodic memory, and semantic network theory
Memory • Memory consists of a collection of complex interconnected systems, each serving different purposes and operating in very different ways. • We do not have a singular memory – we have different memory systems. • However the one function that all these memory systems have in common is storing information for future use. • Box 6.1 – An Extraordinary Memory, pg. 287 • Learning Activity 6.1 – Thinking about memory, pg.287
Defining Memory • Memory is very closely related to learning, if no learning was to occur there would be nothing to remember • Memory is essentially an internal record or representation of some prior event or experience • Most psychologists view memory as an active information processing system that receives, organises, stores and recovers information • Although the human brain is more sophisticated than a computer – the way in which our memory works can be likened to that of a computer and MS Windows • They are comparable because they handle information in a sequence involving three key processes
Defining Memory • The conversion or encoding of information into a useable form. • The retention or storage after it has been encoded. • It’s recovery or retrieval when needed.
Defining Memory • Information that is received and stored in memory must be converted from its raw sensory state to a form that the brain can use or process. • New information must also be placed, or represented in some form – sound, vision, touch or meaning – in the memory system.
Defining Memory • The entire process of converting information for storage and representing it in memory in a useable form is called encoding. • Storage is the retention of information over time. This almost always occurs in the brain (except muscles – neuromuscular patterning). • Finally information is retrieved or located and taken out of storage, when needed. Retrieval is the process of locating and recovering the stored information from memory.
Defining Memory • When human memory works effectively – encoding leads to storage and storage enables retrieval. • Box 6.3 – Automatic and Effortful Encoding, pg. 291 • Learning Activity 6.2 – Review questions, pg. 292
Models for Explaining Human Memory • Like many complex phenomena and constructs, psychologists break down memory into components which can be studies separately from one another and consider how each component contributes to an understanding of the whole • A model is then used to represent, describe and explain memory and its components and processes • Three models of memory we will examine include • Atkinson and Shiffron’s (1968) multi-store model • Baddeley and Hitch’s (1974) model of working memory • Craick and Lockhart’s (1972) levels of processing framework
The Atkinson-Shiffron multi-store model • The Atkinson-Shiffron multi-store model represents memory as consisting of three distinguishable components known as the sensory register, the short term store and long term store • The three components are represented as separate memory stores through which information is transferred • Each component stores, encodes, and processes information in different ways, but they operate simultaneously and interact
The Atkinson-Shiffron multi-store model • Atkinson and Shiffron described the sensory register is the entry point for information into memory from the external environment • It stores vast quantities of information for up to several hundreds of milliseconds • Any information in the sensory register that is attended to is transferred to the short-term store; if the information is not attended to its neural imprint decays and is lost forever • Atkinson and Shiffron also determined that there may be different types of sensory registers for visual and auditory information
The Atkinson-Shiffron multi-store model • The short-term store has been described by Atkinson and Shiffron as ‘temporary working memory’ in which we manipulate information that is held to perform everyday functions • The short-term store receives inputs of information from the sensory register as well as information retrieved from the long-term store • However unlike the sensory register and long-term store the short term store only has a limited capacity – around 7 bits of information at a time • Information can only be held there for 30 seconds or so unless a conscious effort is made to keep it there longer via a process such as rehearsal
The Atkinson-Shiffron multi-store model • Atkinson and Shiffron described the long-term store is described as holding information relatively permanently in a highly organised way and having an essentially unlimited capacity • Unlike the sensory register and the short-term shore, information in the long-term store does not usually decay and can last a lifetime
The Atkinson-Shiffron multi-store model • An important aspect of the Atkinson-Shiffron multi-store model is its description of human memory in terms of its structural features and its control processes • Structural features are the permanent, built-in fixed features of memory that do not vary from one situation to another – for example the three different stores are structural features • Control processes are selected and used by individuals and may vary across situations – examples of control processes are attention and rehearsal
Limitations of the Atkinson-Shiffron multi-store model • Although published 40 years ago the multi-store model of memory played a large role in shifting the view that memory was a singular system • Some of the model, however, has been challenged or refuted based on newer research and ideas • It is now clear that information does not simply ‘flow’ from the sensory register through the short-term store and into the long-term store • There is also much evidence that there is separate sensory registers for sound, vision, touch and maybe other senses – these are now collectively referred to as a sensory memory system
Limitations of the Atkinson-Shiffron multi-store model • The short term store is now viewed as a more complex system which we term working memory • The long term store or long term memory as it is now commonly known, is also thought to contain many different types of memory rather than a singular system • These sub-systems each process and store a different type of memory such as procedural or episodic memories • Learning Activity 6.3 – Review questions, pg. 295 • Learning Activity 6.4 – Visual presentation summarising Atkinson and Shifron’s three components of memory, pg. 296
Sensory Memory • Sensory Memory is the entry area of memory – the initial part of the memory system where all the stimuli that bombard our senses are retained in their original sensory form for a very brief time. • It is believed that sensory memory holds more information than we can actually ever use or remember. • Thus sensory memory is assumed to have an unlimited capacity.
Sensory Memory • Sensory Memory stores all incoming sensory information in separate memory sub-systems called sensory registers, and each register receives and stores sensory information from specific sensory receptors. • The ability to retain sensory information for a brief period gives us additional time to process and encode this information into a more lasting form.
Sensory Memory • Any stimulus that is absorbed into our sensory memory is available to be selected for attention and for processing into a more permanent type of memory. • If the information is not attended to and no further processing occurs, it simply vanishes from experience. • Under most circumstances we are not aware of our functioning sensory memory.
Iconic Memory • Iconic Memory is the name given to visual sensory memory, or the memory of visual sensory information. • Visual images in their original sensory form are usually retained in iconic memory for about 1/3 of a second, but they last long enough for identification of the stimulus to begin. • If iconic memory lasted longer than this, images would begin the overlap and your perceptions of the world would become distorted • If you light a sparkler and draw an imaginary circle around your with the tip, you will perceive a circle – this recognition of a circle is possible because iconic memory holds the image of the tip of the sparkler very briefly in each position of the circle
Iconic Memory • The existence of a sensory register for visual input was first demonstrated by psychologist George Sperling (1960). • Sperling’sExperiment, pg. 298-299 • Learning Activity 6.5– Evaluation of research by Sperling (1960), pg. 299 • Subsequent research by other psychologists have found that the typical duration of iconic memory is about 0.3 seconds. • Box 6.4 – Photographic Memory Activity, pg. 299
Echoic Memory • Echoic Memory is the name given to auditory sensory memory, or the memory of auditory sensory information. • It is called echoic memory because sounds linger in it like an echo. • To experience echoic memory, clap your hands once and notice how the sound remains for a very brief time and then fades away.
Echoic Memory • Studies on echoic memory indicate that it functions like iconic memory, storing sounds in their original sensory form. • The main difference however, is that echoic memory stores information for longer periods (usually 3-4 seconds). • This time period is generally long enough to select what has been heard for interpretation before the sounds completely disappears.
Echoic Memory • Example – Watching TV and being asked a question. • Echoic memory is necessary to comprehend many sounds, particularly those involved in speech. • You cannot comprehend a word until you have heard all the sounds, so auditory information must be stored for sufficient time until all the sounds involved have been received. • Example – The words ‘mallet’ and ‘malice’. • If echoic memory was as brief as iconic memory, speech might sound like a series of separate distinct sounds instead of words and phrases.
Sensory Memory • Information is lost and replaced so rapidly in the sensory registers that we are rarely aware of our capability for storing information. • It also seems that sensory memory acts as a kind of filter for information, keeping out irrelevant and unimportant information, while keeping important or vital information. • Considering the many billions of bits of information detected by our senses in a lifetime, processing everything that reaches sensory memory would probably lead to confusion, frustration and inefficiency in daily living.
Sensory Memory • When walking through the city, your echoic memory will register thousands of different sounds but you will attend to and remember a select few. • If crossing Flinders Street, you hear the screech of car brakes nearby, you will probably pay to and act on that information because of the potential threat to your safety. • At that moment when you are attending to processing the sound of the brakes, you will ignore other sounds which enter echoic memory such as people talking and other cars.
Sensory Memory • When you attend to a sensory stimulus, it is transferred to short-term memory. • Only the information selected for passage into short-term memory receives further processing and has a chance of being stored permanently. • Information that is not attended to from sensory memory is lost very quickly (a few seconds at most).
Sensory Memory • Box 6.5 – Tactile Sensory Memory, pg. 302 • Box 6.6 – Déjà Vu, pg. 303 • Learning Activity 6.6– Review questions, pg. 304
Short-term Memory • When you pay attention to information in your sensory memory (or information retrieved from long-term memory), the information enters your short-term memory. • For example – as you read this sentence it has entered your short-term memory because you are paying attention to it. • Short-term memory holds all the information you are consciously thinking about at any moment of time.
Short-term Memory • Short-term memory (STM) is a memory system with a limited storage capacity in which information is stored for a relatively short period of time. • In STM, the information is no longer an exact replica of the sensory stimulus but an encoding or representation of one, such as a word or number. • Generally items in STM can be retained fairly well for the first few seconds, but after 12 seconds recall is poor and at 18 seconds the information disappears entirely if it has not been renewed.
Short-term Memory • Likewise to complete a sum in your head (23 x 7), you need to be able to temporarily store the numbers to complete the necessary operations. • Depending on what we select for attention, once information reaches STM, a number of things can occur – the information can be discarded, it can be encoded, or it can be rehearsed for a while. • If you rehearse the information it will be retained in STM for as long as the information continues to be rehearsed.
Short-term Memory • For example – consider a situation where you look up a phone number to call someone. • If you ring and get an engaged tone, you will need to rehearse (repeat) the number in your head to keep it in STM until you ring again and the phone is answered. • When you have made the call, you no longer need it and it will be quickly discarded.
Short-term Memory • We hold information in STM long enough to evaluate it, organise it and combine it with both new information and old information retrieved from storage. • Thus, STM can be thought of as a limited working memory that is used in two ways: • To select and process ongoing information. • To store memories for short duration.
Duration of Short Term Memory • Most types of information in the STM can be held quite well for the first few seconds • After about 12 seconds however, recall starts to decline and after about 18 seconds almost all of the information disappears entirely if it has not been attended to • Famous research by Peterson & Peterson (1959) demonstrated that the STM has a duration of around 18 seconds when information is not attended to
Capacity of STM • Compared to sensory memory and long term memory, short term memory is very limited in storage capacity; that is, the amount of information it can hold at any one time. • Read the following numbers and write them down on a piece of paper without looking: • 7, 2, 9, 4, 1, 8, 3 • How many did you get right?
Capacity of STM • Now do the same with the following set of numbers: • 4, 9, 1, 7, 3, 8, 6, 2, 9, 5, 7 • How many did you get right?
Capacity of STM • If you have average STM recall, you will probably be able to recall the seven numbers in the first set, but not all of the numbers in the second • US Psychologist George Miller (1953) described that our STM can handle about ‘7 bits’ of information at any one time – plus or minus 2 • Therefore our STM capacity is best described as 7 + 2 items of information • Information in STM is lost primarily due to decay (not being used or attended to) and displacement (being pushed out by new information)
STM as Working Memory • STM is also involved in interpreting and analysing information (mental work) such as when we make decisions, solve problems and comprehend written and spoken language • Because STM provides a place for mental work, psychologists also refer to STM as working memory – a kind of mental workbench that allows us to manipulate or work with information • The term working memory is used to emphasise the active part of our memory where information we are aware of is actively ‘worked’ on in a variety of ways • For example – If you are to understand a sentence, you need to remember the beginning of the sentence until you get to the end • Learning Activity 6.7 – Review questions, pg. 307
Chunking and STM • Chunking is the grouping or packing of bits of information into larger units that can be remembered as single units • Chunking expands STM by making large amounts of information more manageable • Chunks can take any form. They can be numbers, images, words, sentences, phrases or abbreviations (VCE, RACV, CSIRO)
Chunking and STM • We usually find it easier to remember numbers in chunks than as a string of single digits • 3195287451 • 319-528-7451 • To overcome the limited capacity of STM, chunking can increase the amount of information entering by increasing the amount of information in each chunk • Learning Activity 6.9 – Practical activity on chunking, pg. 309
Rehearsal and STM • Information can be kept in STM for longer than the usual maximum 18 seconds by rehearsing the information in some way. • Rehearsal is the process of doing something so that information can be retained in memory and then retrieved when required.
Rehearsal and STM • Rehearsal may be: • Vocal – saying something over and over aloud. • Sub Vocal – silently repeating information in ‘your head’. • Verbal – doing something that involves the use words. • Non Verbal – maintaining an image of something after it has been seen. • The two main types of rehearsal are called maintenance rehearsal and elaborative rehearsal.
Maintenance Rehearsal • Maintenance Rehearsal involves simple, rote repetition of information being remembered to retain that information in STM. • When you hear something for the first time and go over it so you don’t forget it – you are using maintenance rehearsal. • Studies indicate that most people tend to favour speech, either covert (in their head) or overt (out aloud) for rehearsing the contents of STM.
Maintenance Rehearsal • Although maintenance rehearsal can be very effective, it does not always lead to long-term retention. • Nonetheless, maintenance rehearsal is an important task for coping with limited duration of STM. • One drawback is that when new information is continually entering STM, the amount of new information that can enter is restricted because of the limited storage capacity of STM. This in turn restricts the amount of information that is then transferred to LTM.
Elaborative Rehearsal • To transfer information to long term memory, where it can be stored indefinitely, it would be more effective to use elaborative rehearsal. • Elaborative Rehearsal generally involves organising and dealing with new information in terms of its meaning. • More specifically, elaborative rehearsal is the process of linking new information in a meaningful way with information already stored in memory or with other new information, to aid in its storage and retrieval from LTM.