Introduction
This is the second part of a study of these two articles.
What are the differences between long-term, short-term, and working memory? By Nelson Cowan
50 years of research sparked by Atkinson and Shiffrin (1968) By Kenneth J. Malmberg & Jeroen G. W. Raaijmakers & Richard M. Shiffrin
Context
It is possible to distinguish short term memory and long term memory in two ways.
Duration and Capacity
However, a clear division hasn’t been found yet due to the complex mechanism of human memory.
Duration
While long term memory lasts forever ( though we may not always feel like it does ), short term memory is subject to decay with time.
This decay is what causes it to disappear before having enough time to become a long term memory.
This time limit is a dominant limiting factor in serial recall or short lists (≈ lower amounts of information) conditions.
Serial recall
= memory task that demands the retrieval of information in a specific order
Ex : phone number
Our mechanism against this is rehearsal.
Rehearsal
= Rethinking of an item at any time after it’s presentation
The original theory and many current ones state it as what links short term memory to long term memory :
Rehearsal takes information from the long term memory into the short term memory and,
Makes information in the short term memory stronger to eventually make a place for it in long term memory.
To give an answer to the question of how long short term memory is, the length of short term memory, without rehearsal, needs to be measured.
The problem with rehearsal is :
Rehearsal can be done effortlessly and unconsciously
It will happen if it isn’t prevented with some kind of activity. Even when trying to measure only short term memory.
The first way of preventing rehearsal is called articular suppression
Articular suppression
= repeatedly saying a simple word, like “the”, when being shown the list and during the transaction to the test
Used in verbal list memory tasks where the participants are shown a list of words in order
It is possible , however, that this causes interference
Interference
= information that comes before or after the main information and will disrupt the memorisation process of it
Another way of preventing rehearsal is attention demanding tasks
Attention demanding tasks
= tasks that use the attention of an individual
When the attention of the participants are towards something else, no rehearsal of the measured information will happen
The tasks are shown to cause a degree of interference proportional to the time of the tasks
This means it could be possible to calculate the length of the memory by subtracting the amount of interference
Even if we were able to remove rehearsal, it wouldn’t be 100% short term memory.
The information created directly from sensing something is short term memory.
But, the brain will look for similar things in past memories and bring the information out. These are long term memories.
When presented with a list of words, the words that are presented early will be stored in a more long term memory while those at the end of the list will be stored in short term memory.
This has been proven in patients with Korsakoff’s amnesia who were only able to remember the end of the list if tested immediately after.
Korsakoff’s amnesia
= a disorder which cause issues in memory formation and long term memory
It is caused by a deficiency in vitamin b and is generally associated to alcohol abuse and malnutrition
For the control group, the end of the list was remembered even after a delay.
This is called the recency effect, a form of temporal distinctiveness.
The items at the start of a list, in contrast, have been found to activate areas in the hippocampal system related to long term memory retrieval
Recency effect
= a trait if human cognition where items that are presented last are better remembered
Could also be because of :
- Less time for decay to occur
- Less interference
Temporal distinctiveness
= when the timing of an item will help its retrieval
Back to the first part : Memory, from fractions of a second to an eternity. Also is memory = intelligence?
Next Part : How much can we keep in short term memory ?
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