Long-term memory

When information enters the memory system from sensory input, it must be changed into a format that the system can understand, so it can be stored. There are 3 main ways in which information can be coded:

• Visual (picture)
• Acoustic (sound)
• Semantic (meaning)

Evidence suggests that the principle coding system in short-term memory is acoustic coding. When a person is presented with a list of numbers or letters, they will try to hold them in STM by rehearsing them. Rehearsal is a verbal process regardless of whether the list of items is presented acoustically or visually.

The principle encoding system in long-term memory appears to be semantic coding. However, information in LTM can also be coded visually and acoustically.

Encoding phases in psychology experiments are usually tasks of encoding a word list, pictures, videos etc.

This concerns the nature of memory stores, i.e where the information is stored, how long the memory lasts for, how much can be stored at any time, and what kind of information is held.

Most adults can store between 5 and 9 items in their short-term memory. Miller (1956) called it the "magic number 7" saying that short-term memory capacity was 7 +/- 2.

If we chunk information together we can store a lot more information in our short-term memory. In contrast, the capacity of LTM is thought to be unlimited. Information can only be stored for a brief duration in STM (0-30 seconds), but memories stored in LTM can last a lifetime.

This refers to getting information out of storage. If we can't remember something, it may be because we're unable to retrieve it. When asked to retrieve something from memory, the differences between STM and LTM become very clear.

STM is stored and retrieved sequentially. For example, if given a list of words to remember and then asked to recall the fourth word on the list, you would go through the list in the order you heard it in order to retrieve the information. LTM is stored and retrieved by association. 

Organising information can help aid retrieval. You can organise information in sequences, such as alphabetically, by size, or by time.

Testing the theory: Craik & Tulving (1975)

Procedure - encoding phase

• Participants given a non-memory task which forces them to process stimuli at a particular level
• This 'incidental learning' paradigm is important; it allows control over the types of processing engaged during encoding
• Structural processing had a 16% recognition rate, phonological had a 57% rate, and semantic had a 78% rate.

Applied implications

• Elaborate rehearsal involves deeper processing than maintenance rehearsal, and is more effective in transferring information into long-term memory. Organise and understand material rather than just memorising it.

It is impossible to separate encoding and retrieval. There is a need to consider the effect of the relationship between encoding and retrieval stategies on performance

Morris et al (1977)

Encoding phase

• Semantic: processing the items semantically
• Phonological: making rhyme judgements

Retrieval phase

• Semantic: standard recognition test - which word have you seen before? 
• Phonological: rhyme recognition test - which of these words rhymes with a word you've heard before
• Better standard recognition after semantic encoding, better rhyme recognition after rhyme encoding

Tulving & Thompson (1973): The probability of recall depends on how closely the context at test time matches the context that was present during encoding. The emphasis is on the amount of contextual overlap. These conditions may refer to the context in which the information was encoded, the physical location or surroundings, as well as the mental or physical state of the individual at the time of encoding.

• Intrinsic context: information that is encoded with a target that relates to the target's meaning
• Extrinsic context: physical surroundings or conditions during encoding

Light & Carter-Sobel (1970) studied intrinsic context

• Encoding phase: "the strawberry jam tasted great"
• Retrieval phase: "do you recognise the underlined word" - same context: strawberry jam. different context: traffic jam
• There was an improvement in recognition when the word was presented in the same context

Baddeley & Godden's context cue study examined extrinsic context

Memory is a network of associated ideas, concepts, and information. When people think about, or try to remember one piece of information, there's a 'spreading activation' of related concepts throughout the network that helps you remember more.

A retrieval cue activates information stored in memory. The more retrieval cues you have, the more chance you have of accessing the target information you want to retrieve.

Elaborate encoding: increased number of self-generated cues associated with the information you're trying to remember
Encoding specificity: increased number of context-related cues associated with the information you're trying to remember

Applications

• Mental reinstatement of context: encourages an eyewitness to mentally recreate the psychological and physical environment which existed at the time of the event.