Memory

Memory is the faculty of the mind by which information is encoded, stored, and retrieved (Atkinson & Shiffrin, 1968). Memory is essential to experiences and related to limbic systems, it is the retention of information over time. If we couldn't remember past events, we couldn't learn or develop language, relationships, nor personal identity.

• "A man's memory is all that stands between him and chaos" - A.L. Korsakoff
• "You have to begin to lose your memory, if only in bits and pieces, to realise that memory is what makes our lives. Our memory is our coherence, our reason, our feeling, even our action. Without it, we're nothing." - Luis Buñel

Memory is often understood as an informational processing system made up of a sensory processor, short-term (or working) memory, and long term memory. It has explicit and implicit functions.

Clive Wearing suffers from chronic anterograde and retrograde amnesia. He lacks the ability to form new memories, and cannot recall aspects of his past memories, frequently believing that he has only recently awoken from a coma.

In 1985, Wearing contracted herpesviral encephalitis, a virus that attacked his central nervous system. From that point, he has been unable to store new memories. The virus caused damage to the frontal and temporal lobe, specifically the hippocampus, an area required to transfer memories from short-term to long-term memory. He is completely unable to form lasting new memories - his memory only lasts between 7 and 30 seconds.

Despite the retrograde and anterograde amnesia, he still recalls how to play the piano and conduct a choir, because his procedural memory was not damaged by the virus.

William James (1890): attempted to delineate memory systems in terms of the relationship of their contents to conscious awareness

• Primary memory (STM): conscious memory for what we're thinking about now. Information is in an active state
• Secondary memory (LTM): Information is in an inactive state. It is an unconscious repository of information

Evidence for separate LTM and STM systems:

• Difference in capacity - digit span demonstration. Miller (1956) consistently demonstrated that people have a digit span of 7 +/- 2. The signature capacity of STM is 7 +/- 2. LTM on the other hand has no known limit to its capacity.
• Primacy and recency effects - serial position task. Glanzer & Kunitz (1966) asked participants to recall a list of words in any order. The primacy effect (first words are remembered well) occurs because early words are rehearsed more and enter LTM. The recency effect (last words are remembered well) occurs because later words are still in STM

Neuropsychological evidence

• Amnesic patients: Henry Molaison had chronic epilepsy. He was treated by having his brain bilaterally severed, almost completely removing the hippocampus (same region destroyed in Clive Wearing's brain). It controlled his epilepsy but led to profound memory impairments

Long term memory problems

• Henry Molaison suffered from severe anterograde amnesia (failure to form new memories). He suffered retrograde amnesia for some events before epilepsy surgery. However, his short-term memory was relatively spared. He still performed well on digit-span tasks

Multi-store model of memory (Atkinson & Shiffrin, 1968): a structural model

• They proposed that memory consisted of 3 stores - sensory buffer, short-term memory store, and long-term memory store. Information passes from store to store linearly, and has been described as an information processing model (input, process, and output).
• Information from the environment enters the sensory buffer. If it is attended to, it passes into the short-term memory store and is held for up to 20 seconds. If the information is rehearsed, it can pass into the long-term memory store.
• The short-term memory store has a duration of 5-20 seconds. Its capacity is 7 +/- 2 items.
• The long-term memory store's abilities are more unknown. Duration of items is thought to be unlimited, similarly to its capacity.

Levels of processing - Craik & Lockhart (1972)

• They disagreed with the modal structure. The levels of processsing model focuses on the depth of processing involved in memory, and predicts that the deeper the information is processed, the stronger the memory trace will be.
• We can process information in 3 ways:
• (1) - structural processing. This processing is based on encoding the physical qualities of something e.g the font of a word
• (2) - phonological processing. This is when we encode something's sound. Structural and phonological are both forms of shallow processing
• (3) semantic processing. This is based on encoding something's meaning. It is deep processing and results in a strong memory trace
• We also have a central processor which is where maintenance rehearsal (repetition to hold something in the STM) and elaboration rehearsal (which involves a meaningful analysis and strong memory) takes place

Evaluation

• The model is oversimplified, suggesting that both short-term and long-term memory operate in a single, uniform fashion. It is also unlikely that different kinds of knowledge are all stored within a single, long-term memory store
• Rehearsal is considered too simple to account for the transfer of information from STM to LTM
• We don't deliberately rehearse some experiences, yet we can remember them, e.g what you had for dinner last night
• STM seems to be different for visual and auditory
• Repeated presentation to STM should lead to good memory as it is rehearsal, but this isn't always true. For example, recall of details of common coins is poor.