Types of long-term memory
Specification: Types of long-term memory: episodic, semantic, procedural.
Atkinson & Shiffrin’s (1968) multi‐store model is often criticised for being too simplistic. Although they made a distinction between a sensory register (SR), short‐term memory (STM) and long‐term memory (LTM), they provided no detail of the memory processing within each store. The Working Memory Model (WMM) proposed by Baddeley and Hitch (1974) divided STM into two separate subcomponents: the phonological loop and the visuo‐spatial sketchpad [see next section]. In addition, psychologists have suggested that there are multiple types of LTM, including: episodic, sematic and procedural.
Although there are at least three types of LTM (episodic, semantic and procedural), all long‐term memories are categorised as either explicit (declarative) or implicit (non‐declarative). Explicit memories include knowledge for events and facts (knowing that), whereas implicit memories are skilled behaviours (knowing how), which are largely unconscious.
Episodic memory
Episodic memory is a type of explicit memory, which includes memories of personal experiences
(episodes), such as your first day at school or when you last visited the doctor. These memories are more complex than you might consider and have three specific elements including: details of the event; the context; and emotions, which are all interwoven to provide a single memory.
The strength of episodic memories is determined by the strength of the emotions experienced when the memory is coded, and a conscious effort is required to retrieve them. Episodic memories are associated with the hippocampus, although other areas of the brain regions are associated with coding (prefrontal cortex).
Semantic memory
Semantic memory is also a type of explicit memory, which includes memory for knowledge, facts, concepts and meaning about the world around us. For example, knowing that London is the capital of England is an example of a semantic memory and so too is knowing that the legal age to drive in the UK is 17 years old.
Semantic memories often start as episodic memories, as we acquire knowledge based on our personal experiences, but they are not ‘time‐stamped’ in the same way nor do they remain closely associated with a particular event (episode). Like episodic memories, the strength of semantic memories is determined by the strength of the emotions experienced when the memory is coded, although semantic knowledge is often less personal in its nature and can relate to abstract concepts such as language and maths. However, semantic memories are generally stronger in comparison to episodic and are associated with the temporal lobe.
Procedural memory
Procedural memory is a type of implicit memory, which includes memory of how to perform certain tasks, actions or skills, such as swimming, reading and writing which have become ‘automatic’.
Procedural memories are implicit and therefore difficult to explain in words to someone else. They are often acquired through repetition and practice, for example, when we learn to ride a bike or drive a car. Many procedural memories are formed early in life, for example, walking. It is important that these become like second nature to us so that we can focus our direct attention onto other everyday tasks we perform at the same time. (Imagine walking with a friend, and having to stop every time you wanted to say something!) Procedural memories are associated with the cerebellum and motor cortex.
Evaluating Long Term Memory
Brain scans provide support for the different types of LTM. Research has shown that different parts of the brain are active when accessing episodic, semantic and procedural memory. Episodic memory has been associated with the hippocampus and temporal lobe; semantic memory is also associated with the temporal lobe; and procedural memory is associated with the cerebellum and motor cortex. Brain scan research suggests that different brain regions are responsible for the different types of LTM, supporting the idea that our LTM is made up of at least three distinct categories.
Support for the distinction between implicit and explicit LTM comes from the case study of patient HM (Milner, 1962). Patient HM suffered from severe epilepsy and underwent surgery, which involved the removal of his hippocampus, to alleviate the symptoms. His STM remained intact; however, he was unable to transfer certain types of information to his LTM. Milner discovered that HM was able to learn procedural (implicit) tasks, but not episodic or semantic (explicit) information. HM was able to learn a mirror‐tracing task, where you copy an image while looking in a mirror, and retain the skill without forgetting. However, he had no knowledge of ever previously completing the mirror‐tracing task. Therefore, HM was able to demonstrate his procedural memory through implicit behaviour, despite being unable to recall his experience explicitly.
Further support for the distinction of implicit and explicit memory comes from a separate case study of Patient PM (Finke et al. 2012), a cellist who suffered from amnesia as a result of a virus. Like patient HM, his implicit memory (episodic and semantic) memory was affected, but his procedural memory for reading and performing music remained intact. PM demonstrates a clear distinction between different types of LTM. Although both HM and PM provide support for the distinction of separate types of LTM, evidence from case studies must be treated with caution. It is difficult to establish exactly which brain regions are affected in patients with brain damage and damage to a particular region (for example, the hippocampus) does not necessarily mean that region is associated with a particular type of memory.
Understanding different types of memory allows for the development of helpful real world applications. Belleville et al. (2006) compared the performance of older people suffering with a mild cognitive impairment who received memory training with that of a control group who did not. It was found that participants in the experimental group performed better on a test of episodic memory. This suggests that being able to identify different types of LTM can provide psychologists with the opportunity to improve peoples’ lives though devising appropriate treatments.