Types of Long-Term Memory

The MSM has a major limitation of the fact that it says that long-term memory is a unitary store, but on the basis of may different psycological studies, many psychologists believe that there are potentially many different long-term memory stores.

Tulving (1985) was one of the first cognitive psychologists to realise that the MSM's view of LTM was too simplistic and inflexible.

He proposed that ther were in fact three different LTM stores, containing quite different types of information.

Episodic memory refers to our ability to recall events (episodes) from our lives such as your first day at school.

These memories sre much more complex than they appear.

Firstly they are time stamped so you remember when these things happened.

Secondly, your memory of single episodes will include several elements, such as people and places, objects and behaviours, all of them interwoven to produce a single memory.

Thirdly, you have to make a conscious effort to recall episodic memories. Even though you may be able to do this quickly, you are still aware that you are searching for your memory of an event.

Semantic memories contain our knowledge of the world. This type of memory has been compared to the likes of an encyclopedia and a dictionary.

Semantic memories are different to episodic memories as they are NOT 'time-stamped'.

Semantic knowledge is less personal and more about facts we all share but, semantic memory is much more about facts as it contains an immense collection of material which is constantly being added to.

Procedural memory is our memory for actions, or skills, or how we do things.

We can recall these meories without conscious awareness or a great deal of effort.

An example of this would be driving a car. Eventually our ability to do this comes from our procedural memory and we start to do things such as changing gear without realising that we have done it.

STRENGTH

A strength of episodic memory is that it is supported by case study evidence as clinical studies of amnesia (HM and Clive Wearing) showed both had difficulty recalling events that had happened to them in their pasts.

However, their semantic memories were relatively unaffected (e.g. HM did not recall stroking a dog half an hour ago but he did not need the concept of 'dog' explaining to him.)

This supports the view that there are different memory stores in the LTM because one store can be damaged but the others can be left unaffected.

STRENGTH

A strength is that brain scan studies show that there are different LTM stores.

Tulving (1994) had participants perform various memory tasks while their brains were scanned with a PET scanner.

Episodic and semantic memories were in the prefrontal cortex; semantic in the left side and episodic in the right prefrontal cortex.

This shows a physical reality in the brain to the different types of LTM, confirmed in many research studies, supporting its validity.

STRENGTH

A strength is that identifying different types of LTM stores has real-life applications.

Psychologists can target certain kinds of memory in order to improve people's lives.

Belleville et al. (2006) found that episodic memories can be improved in older people with mild cognitive impairments.

Training lead to improvements (compared to a control group).

This highlights the benefits of distinguishing between different types of LTM- it allows specific treatments to develop.

LIMITATION

A limitation is that there are many different problems with clinical evidence.

Evidence is often based on clinical studies, such as HM and Clive Wearing, about what happens when memory is damaged,

There is a serious lack of control of different variables in these studies (e.g. cannot control the precise location of the brain damage or personality variables).

This means that it is difficult to generalise from these case studies to determine the exact nature of LTM.

LIMITATION

A limitation of Tulving's approach is that there may only be two types of LTM.

Cohen and Squire (1980) argued that episodic and semantic memories are stored together in one LTM store called declarative memory (memories that can be consciously recalled).

Cohen and Squire agree that procedural memory is a distrinctly different kind of memory to semantic/episodic, and call it non-declarative.

It is important to get the distinction between semantic and episodic memories right because the way we define them influences how memory studies are conducted.

Episodic Memory- a LTM store for personal events. It includes memories of when events occured and of the people, objects, places and behaviours involved. Memories from this store have to be retrieved consciously and with effort.

Semantic Memory- a LTM store for our knowledge of the world. This includes facts and out knowledge of what words and concepts mean. These memories usually also need to be recalled deliberately.

Procedural Memory- a LTM store for our knowledge of how to do things. This includes our memories of learned skills. We usually recall these memories without making a conscious or deliberate effort.