The features of memory Flashcards
What is memory?
The process by which we retain and recall information about events that have happened in the past
What is the STM
Your memory for immediate events, which disappears if not rehearsed
What is the LTM?
Your memory for events that have happened in the past, from anywhere between 2 minutes and 100 years ago. It is the permanent memory store
What is a sensory register?
A huge store of information from our senses for a very brief amount of time (about half a second)
What is the capacity of STM?
Limited capacity
According to Jacobs (1887), on average people can store between 9.3 numbers and 7.3 letters
According to Millers (1956), we used STM by chunking so we can chunk 7 (+/- 2) items
What is the duration of the STM?
Limited - up to 30s without rehearsal
Peterson and Peterson found information must be rehearsed (but using consonant trigrams) in order to keep it in the STM and it has a limited duration of 30s when rehearsal is prevented. Shows STM is different to LTM
How is STM coded?
Acoustically
Baddeley (1966) - the group trying to memorise acoustically similar words, immediately after being told them did the worst, implying the acoustic coding
What is the capacity of the LTM?
Potentially unlimited
What is the duration of the LTM?
Potentially up to a lifetime
Bahrick et al. (1975) - within 15 years of graduation recognise 90% and recognise 70% after 48 years. Free recall within 15 years of graduation 60%, and 30% after 48 years
How is LTM coded?
Semantically
Baddeley (1966) - the group that tried to memorise semantically similar words, 20 mins after being told them did the worst, implying the semantic coding
Strength/weakness of Jacobs’ study (capacity)
May have lacked control (old) e.g. distractions acting as a confounding variable so not internally valid and may have underestimated the capacity
Has been supported by other researchers, so confirms its validity
Weakness of Miller’s study (capacity)
Cowan (2001) disagreed with Miller, suggesting that the capacity of STM is 4 chunks, so Millers lower estimate may be more valid
Strength and weakness for Peterson and Peterson (duration)
Artificial stimuli - not externally valid as we don’t typically try to memorise meaningless info
Controlled - same length and difficulty for participants so greater internal validity
Strength/weakness for Bahrick et al. (duration)
Higher external validity due to use of real-life memories and so tells more than artificial studies
Confounding variables of whether they looked at yearbooks over the years which weren’t controlled
Weakness for Baddeley (coding)
Artificial stimuli - words have no real meaning for participants so if given more meaningful info, the recall of STM and LTM may be different
Jacobs’ (1887) study procedure and findings
Jacobs (1887) developed a technique to measure digit span. The researcher gives, for example, four digits and then the participant is asked to recall these in the correct order out loud.
If this is correct, the researcher reads out five digits, and so on until the participant cannot recall the order correctly.
This determines the individual’s digit span.
Jacobs found that the mean span for digits across all participants was 9.3 items. The mean span for letters was 7.3.
Miller’s (1956) study procedure and findings
From a review of psychological research, Miller (1956) found that the span (capacity) of human memory is about 7 items (plus or minus 2).
People cope well with counting 7 flashing dots but not much more – same for digits, numbers and even words. He also noted that people can recall 5 words as easily as 5 letters.
They do this by chunking – grouping sets of letters or digits into units or chunks.
Peterson and Peterson’s study procedure and findings
A lab experiment was conducted in which 24 undergraduate students took part in 8 trials (8 tests).
On each trial they were given a consonant syllable or trigram (meaningless three-consonant syllables, e.g. TGH) to remember and a three-digit number.
The student was then asked to count backwards from the number in either 3s or 4s until told to stop.
The counting backwards was to prevent any mental rehearsal of the consonant syllable (which would increase the student’s memory).
On each trial, they were told to stop after a different amount of time - 3, 6, 9, 12, 15 or 18 seconds. This is called a retention interval.
After this, they were asked to stop counting and to repeat the trigram.
The percentage of trigrams correctly recalled was recorded for each retention interval.
The longer the interval delay the less trigrams were recalled. Participants were able to recall 80% of trigrams after a 3 seconds delay. However, after 18 seconds less than 10% of trigrams were recalled correctly.
Bahrick et al.’s study procedure and findings
Participants were an opportunity sample of 392 American ex-high school students aged 17-74 years.
High school yearbooks were obtained from the participants directly or from some schools.
Recall was tested in various ways, including: (1) free recall test - where participants recalled the names of as many of their former classmates as possible.
(2) photo recognition test - where they were asked to identify former classmates in a set of 50 where some were from their yearbook and some weren’t.
Participants who were tested within 15 years of graduation were about 90% accurate in photo recognition. After 48 years, recall declined to about 70% for photo recognition. Free recall was less good. After 15 years, this was about 60% accurate, dropping to 30% after 48 years.
Baddeley’s study procedure and findings
Baddeley (1966) gave different lists of words to four groups of participants to remember:
· Group 1 – acoustically similar – words that sounded similar e.g. cat, cab, can
· Group 2 – acoustically dissimilar – words that sounded different e.g. pit, few, cow
· Group 3 – semantically similar – words with similar meanings e.g. great, large, big
· Group 4 – semantically dissimilar – words with different meanings e.g. good, huge, hot
Participants were shown the original list of words and asked to recall them in the correct order. When they had to do this recall task immediately after hearing it (STM recall), they tended to do worse with acoustically similar words. This suggests that information is coded acoustically in STM.
If participants were asked to recall the word list after a time interval of 20 minutes (LTM recall), they did worse with the semantically similar words. This suggests that information is coded semantically in LTM.
