Models of memory

Main features:

• 3 distinct stores; Sensory (SM), Short-term (STM) and Long-term memory (LTM) 
• It is a structural model
• Sensory memory is modality specific
• Information passes from store to store in linear way
• Attention is needed to pass information from SM to STM
• Maintenance rehearsal allows information to be kept in the STM
• Elaborative rehearsal allows information to be passed from the STM to LTM
• Each has its own characteristics of encoding

Primary effect - Higher recall from words at the start of lists, due to rehearsal and transferred to LTM

Recency effect - Higher recall from words at the end of lists,

Primary and Recency effects clearly highlight the existence of 2 seperate memory store.

• Many of the studies of the MSM of memory use laboratory experiments. This helps to control situational variables which may affect attention and thinking, such as noise, heat and light. Also as the laboratory setting makes it easier to control most extraneous variables, it is easier to reliably establish cause and effect.
• However, as many of the studies are in a laboratory setting, it gives a controlled/artificial environment. This means that the findings tend to lack ecological validity. So it may be difficult to generalise the findings to real life situations, therefore telling us very little about how the memory works in real life.
• Can be criticised for being over-simplified with its view of the STM and LTM structures operating in a single uniform fashion.
• Identified a key structure that memory goes through.  

Key study - Miller - STM capacity

Miller used digit span technique in his study on the short term memory. His research evidence showed that there is a limit to the capacity of the short term memory around 5 to 9 (7+/-2) pieces of information. Though, he showed that the capacity can be extended through ‘chunking’, where items are placed into meaningful ‘chunks’. If information in the short term memory is rehearsed, it can be retained in short term storage and then can be transferred to long term memory for potentially indefinite storage. 

Key study - Murdock (1962)

A list of words that varied in length from 10-40 were presented at intervals of 2 seconds for each word. When asked to recall in any order, findings showed more words were recalled from the beginning and end of the list, no matter the length. This showed a Primary and Recency effect. The words from the middle had been displaced from STM but not yet consolidated into LTM, this is strong evidence for the existence of two separate memory stores.

Key study – Wagenaar (1986) – LTM capacity

Wagenaar tested himself on over 2,400 events listed in a diary over 6 year that he had created. Tested on the recall of event, rather than the dates and found that there was an excellent recall of events. This suggests that the capacity of the Long Term Memory is extremely large. However, as this is a long term study on his own memory it’s a very small sample so is difficult to generalise his findings.

Key study – Sperling (1960) – SM

This study can be used to support duration, capacity and encoding. Sperling’s finding in his study showed that information within the sensory memory disappears very quickly. Participants were shown 12 digits/ letters in three rows for 50 milliseconds. When asked to recall 1 row – 75% recall, but if asked to recall all 12 items recall dropped to 42%. This shows that the sensory memory constantly receives large amounts of information which stays for a very short period. Most information receives no attention and disappears/ forgotten. 

Key study – Baddeley (1966) – Encoding

This study investigates coding in short- term and long-term memory. An independent groups design study was carried out with 3 conditions; learning a list of acoustically similar words, semantically similar words and unrelated words. Then were asked to recall them (DV) either immediately (STM) or after 20 minutes (LTM). Findings showed that errors were made mostly in acoustically similar words immediately and semantically similar words after 20 minutes. This shows that acoustic code is used in short term memory and semantic code within long term memory.  

Key Study – Peterson and Peterson (1959) – Duration

Peterson and Peterson gave participants trigrams (e.g. MXT) which they have to recall after varying amounts of time (0-18 seconds). Findings showed that 10% of the trigrams were remembered after 18 seconds, therefore showing that STM is approximately 18 seconds. As information in long-term memory can potentially be stored indefinitely, these findings can be used as evidence for the functional separation of STM and LTM.     

Main feature:

• Only explains Short-term memory
• It's not a structure, it's a process
• Believe it's what happens in rehearsal that is so important
• Proposed words can be processed at a number of levels: Shallow/structural level, Intermediate/phonetic level, Deep/semantic level
• Argued that there are 2 types of rehearsal; maintenance rehearsal (simple repetition) and elaborate rehearsal (analysing the meaning and linking it with stored knowledge in LTM)
• According to Craik and Lockhart - it is the depth of processing that determines the persistence of a memory trace in the LTM
• Elaborate rehearsal = deeper processing

Key study - Craik and Tulving (1975)

Aim: To investigate depth of processing by giving participants a number of tasks requiring different levels of processing and measuring recognition.

Participants were given a list of 60 words, one at a time and were required to process each at 1 of 3 levels (IV): deep level, intermediate level and shallow level. Then participants were given a list of 180 words containing original 60 and asked to identify the ones they were shown.

Findings showed significantly more words were recognised when processed at deep level (65%) then either phonetic (37%) or shallow (17%) levels. This shows that as a deeper processing resulted in better recognition, then the level at which material is processed must be related to memory.

• Study relies on incidental learning, rather than intentional so is more true to real life. This means that participants were unlikely to engage in extra processing which would invalidate results.
• Ethical issues are raised from the deception used with the study.
• Craik later acknowledged that the original levels of processing theory were over-simplified and has accepted a number of research findings.
• Craik and Lockhart argued that perception, attention and memory are interdependent because memory traces are formed as a result of perpetual and attentional processes. They focused attention on these processes and by doing so they have made a major contribution to understanding memory.
• Theory has difficulty in determining what level of processing actually occurs in any particular case. There is no adequate measure of processing depth. Depth is usually defined as 'the number of words remembered' and the 'number of words remembered' is taken as measure of depth.  

Central executive

• Allocates attention to inputs and directs the operation of the other components - not unlike a business executive.
• A flexible system that can process information in any sensory modality in a variety of different ways. Also can store information for brief period of time.
• Focus an switch attention
• Co-ordinate the the subsystems - phonological loop and visuo-spatial scratchpad
• Connects working memory with long-term memory

Phonological loop

• A phonological store, which holds auditory memory traces for a few seconds before fades
• An articulatory rehearsal process, which is essentially sub-vocal speech, and has a limited capacity of about three to four items
• Can be regarded as the 'inner ear' as it remembers vocal sounds in temporal order

Visuo-spatial scratchpad

• A visual component - deals with objects and features such as space and colour
• A spatial component - deals with locations and movements in space

Episodic buffer

• A limited capacity store that binds together information from a number of fields - verbal, visual, spatial and chronological information
• Can use access to the different sub-systems and from conscious awareness. 
• Emerged in 2000, as 3 component model had difficulty explaining the interaction between the working memory and the long-term memory.   
• Allows sub-sytems to interact

• This contemporary model of memory is still being researched and modified, and has provided valuable insighted into the complexity of short-term memory processes.
• Much of the evidence is from laboratory studies. This artificial setting may give a detailed insight into theoretical models but may not generalise to complex real-life situations.
• The concept of the Central executive has remained vague, even as the most important component of the working memory model.
• Imaging studies have produced clear clear evidence that verbal and spatial working memories are seperate. Verbal memories appear to be located in the left hemisphere, whereas spatial memory is located in the right hemisphere of the brain.
• Increasing evidence to support relationship between the phonological loop and acquisition of language (Baddeley). Clinical study of patient with phonological loop deficit found failure to acquire new language.