STM and LTM Flashcards
Short term memory overview
Short-term memory stores and allows recall of information for a period of several seconds up to 30 seconds without rehearsal. Its capacity is very limited.
Long term memory overview
Stores and enables us to recall of information from the more distant past. Its capacity is unlimited and duration is potentially a lifetime.
What are the features of the memory stores?
Durations, Capacity, Coding
Duration
A measure of how long a memory lasts before it is no longer available.
What is the duration of short term memory?
18-30 seconds if not rehearsed
How is information kept in the STM for more than a few seconds?
It is rehearsed (repeated, either aloud or in our heads) to keep it active
Who studied the duration of short-term memory?
Peterson and Peterson (1959)
What was the method of Peterson and Peterson (1959) study?
Participants given consonant trigram and told to count backwards in threes and in intervals of 3, 6, 9 … or 18 seconds they had to stop counting and repeat the trigram
Consonant trigram
3 Random consonants
Why were the participants in Peterson and Peterson (1959) told to count backwards in threes?
So they don’t rehearse the letters
What participants were used in Peterson and Peterson (1959) study?
24 undergraduate students
What were the results of Peterson and Peterson (1959) study?
Participants could remember 90% after 3 seconds, 20% after 9 seconds and less than 10% after 18 seconds.
How much could participants in Peterson and Peterson (1959) remember after 3 seconds?
0.9
How much could participants in Peterson and Peterson (1959) remember after 9 seconds?
0.2
How much could participants in Peterson and Peterson (1959) remember after 18 seconds?
less than 10%
What is the maximum STM duration?
18 seconds
What was the conclusion of Peterson and Peterson (1959) study?
Information decays quickly when not rehearsed and maximum STM duration is 18 seconds
What were the strengths of the Peterson and Peterson (1959) study?
Lab experiment where variables are tightly controlled and procedure can be replicated to ensure reliability
What were the weaknesses of the Peterson and Peterson (1959) study?
- low ecological validity - trigrams presented on earlier trials may have caused confusion
Why was there low ecological validity in Peterson and Peterson (1959) study?
trigrams are unrealistic things to remember and is a rare task to commonly do so it has low ecological validity and doesn’t apply to everyday life
Why is it a weakness of Peterson and Peterson (1959) that the trigrams from earlier trials may have caused confusion?
because we are not sure whether the results gained from the participants were due to them forgetting the trigrams or being confused due to interference
What is the duration of the long term memory?
Up to a lifetime
Who tested the duration of long term memory?
Bahrick et al (1975)
What was the method of Bahrick et al (1975) study?
Participants were tested to see if they could remember they former classmates from pictures, matching names and free recall with no pictures.
What participants were used in Bahrick et al 1975?
400 american participants between 17-74
What was the result of Bahrick et al (1975) study?
After 48 years when asked to link names and faces the accuracy was 70% but when asked to free recall names or classmates the accuracy was 30%
What was the conclusion of Bahrick et al (1975) study?
30-50 years after, participants could still remember classmates showing long term memories can last a lifetime and shows cues give higher chances of recall
What else did Bahrick et al (1975) show other than the fact that long term memories can last a lifetime?
Individuals cannot immediately access all the information stored in their LTM as shown in the free recall task however with cues, recall is higher
What were the strengths of Bahrick et al (1975) study?
High external validity
Why does Bahrick et al (1975) have high external validity?
Because meaningful material was used giving a better estimate of LTM duration. It is an every day task so relevant to real life.
What were the weaknesses of Bahrick et al (1975) study?
- Natural experiment so less control of IV
- Only looked at specific information which may be more meaningful
How was there less control of the IV in Bahrick study due to the format of it being a natural experiment?
It is likely that some of the names had been since rehearsed, showing a confounding variable making the results invalid
Capacity of memory
A measure of the format in which information is stored in the various memory stores, in other words, how much information can be held or stored.
What is the capacity of long term memory?
Unlimited capacity
Who looked at capacity of STM?
Jacobs (1887)
What is the capacity of short term memory?
9 digits and 7 letters, tested by Jacob’s (1887)
What was the method of the Jacobs (1887) study?
Developed the serial digit span technique
Serial digit span technique
the researcher read out 4 digits and the participant was asked to repeat it immediately. more digits were added until the participant could not repeat it back accurately
What was the result of the Jacobs (1887) study?
On average 9 digits and 7 letters were correctly recalled this capacity increased with age during childhood
What is a potential reason for the capacity of the STM increasing with age during childhood?
Because there is a gradual increase in brain capacity as people develop strategies to improve their digit span like chunking
Why may remembering digits in the serial digit span technique by Jacobs (1887) be easier?
Digits may have been easier to recall as there are only 10 digits to remember compared to 26 letters
What are the weaknesses of Jacob’s (1887) study?
- Lacks ecological validity
- Previous sequences recalled by participants may have confused them later on
- Conducted long ago so no way to know if extraneous variables were controlled such as IQ level and distractions during the study
Why does Jacobs (1887) study have low ecological validity?
Because learning random lists of numbers and repeating them back is not a realistic task. More meaningful information may be recalled better and could have given different results
Miller (1956)
Reviewed experiments into short term memory capacity and concluded it was 7+-2 items.
How did Miller (1956) say memory capacity can be increased?
Through a process called chunking
Cowan (2001)
reviewed research and argued that Miller overestimated the capacity of the STM and concluded it was 4 chunks
Coding
Form in which information is stored in various memory stores
What are the three types of coding?
Acoustic, Semantic, Visual
Acoustic coding
storing information in terms of the way it sounds.
Semantic coding
storing information in terms of its meaning.
Visual coding
storing information in terms of the way it looks.
What is the coding for the STM?
Acoustic
What is the coding for the LTM?
Semantic
What did Baddeley (1966) look at?
How the STM and LTM are coded
What was the method of the Baddeley (1966) study?
Participants shown a sequence of 5 words under 1 in 4 conditions and then immediately write them down in order.
What were the conditions of Baddeley’s study?
1) acoustically similar
2) acoustically dissimilar
3) semantically similar
4) semantically dissimilar
What was the first condition of Baddeley (1966)?
Acoustically similar words (map, mad, cad, cap)
What was the second condition of Baddeley (1966)?
Acoustically dissimilar words (pen, cow, pit, day)
What was the third condition of Baddeley (1966)?
Semantically similar words (Tall, high, broad, wide)
What was the fourth condition of Baddeley (1966)?
Semantically dissimilar words (foul, thin, late, safe)
What were the results of the Baddeley (1966) study?
Participants least accurate when tested immediately (STM) on acoustically similar words and when tested 20 minutes after (LTM) they were least accurate with semantically similar words
What was the conclusion of the Baddeley (1966) study?
Information is encoded acoustically in the STM so we find acoustically similar words harder to remember and info is encoded semantically in the LTM so we are more likely to make mistakes remembering semantically similar words
What are the disadvantages of the Baddeley (1966) study?
- Low ecological validity as a meaningless list was used
What are the advantages of Baddeley (1966) study?
Identifies a clear difference in the coding of the two memory stores
