Memory Flashcards
Coding, capacity and duration of memory: Define Short-term memory (STM)
The limited-capacity memory store. In STM, coding is mainly acoustic (sounds), capacity is between 5 and 9 items on average, duration is about 18 seconds.
Coding, capacity and duration of memory: Define Long-term memory (LTM)
The permanent memory store. In LTM, coding is mainly semantic (meaning), it has unlimited capacity and can store memories for up to a lifetime.
Coding, capacity and duration of memory: Define Coding
The format in which information is stored in the various memory stores.
Coding, capacity and duration of memory: Define Capacity
The amount information that can be held in a memory store.
Coding, capacity and duration of memory: Define Duration
The length of time information can be held in memory.
Research on coding- STM and LTM
Baddeley (1966a, 1966b) gave different list of words to 4 groups of participants to remember. These contain words that are acoustically similar and dissimilar and semantically similar and dissimilar.
Participants were shown the original words and asked to recall them in the correct order. When they did this task immediately, recalling from short-term memory (STM), they tended to do worse with acoustically similar words. When they recalled the word list after a time interval of 20 minutes, recalling from long-term memory (LTM), they did worse with the semantically similar words.
These findings suggest that information is coded acoustically in STM and semantically in LTM.
Research on coding (Evaluation: Separate memory stores)
One strength of Baddeley’s study is that it identified a clear difference between two memory stores.
Later research showed that there are some exceptions to Baddeley’s findings. But the idea that STM uses mostly acoustic coding and LTM mostly sematic has stood the test of time.
This was an important step in our understanding of the memory system, which led to the multi-store model.
Research on coding (Evaluation: Artificial stimuli)
One limitation of Baddeley’s study was that it used quite artificial stimuli rather than meaningful material.
For example, the word lists had no personal meaning to participants. So Baddeley’s findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life. When processing more meaningful information, people may use semantic coding even for STM tasks.
This suggests that the findings from this study have limited application.
Research on capacity (Digit span)-STM
Jacobs (1887) found out by measuring digit span. For example, the researcher reads out 4 digits and the participant recalls these out loud in the correct order. If this is correct the researcher reads out 5 digits and so on until the participant cannot recall the order correctly. This indicates 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.
Research on capacity (Digit span)-STM (Evaluation: A valid study)
One strength of Jacobs’ study is that it has been replicated.
The study is a very old one and early research in psychology often lacked adequate controls. For example, some participants’ digit spans might have been underestimated because they were distracted during testing (confounding variable). Despite this, Jacobs’ findings have been confirmed by other, better controlled studies since (e.g. Bopp and Verhaeghen 2005).
This suggests that Jacobs’ study is a valid test of digit span in STM.
Research on capacity (Span of memory and chunking)-STM
Miller (1956) made observations of everyday practice. For example, he noted that things come in sevens: seven notes on the musical scale, seven days of the week, seven deadly sins, etc. Miller thought that the span (i.e. capacity) of STM is about 7 items, plus or minus 2. But he also noted that people can recall 5 words as easily as they can recall 5 letters. We do this by chunking- grouping sets of digits or letters into units or chunks.
Research on capacity (Span of memory and chunking)-STM (Evaluation: Not so many chunks)
One limitation of Miller’s research is that he may have overestimated STM capacity.
Cowman (2001) reviewed other research and concluded that the capacity of STM is only about 4 (plus or minus 1) chunks.
This suggests that the lower end of Miller’s estimate (5 items) is more appropriate than 7 items.
Research on duration (Duration of STM)
Peterson and Peterson (1959) tested 24 students in 8 trials each. On each trial the student was given a consonant syllable to remember. They were also given a 3-digit number. The student counted backwards from this number until told to stop. The counting backwards was to prevent any mental rehearsal of the consonant syllable.
On each trial they were told to stop after varying periods of time: 3, 6, 9, 12, 15 or 18 seconds (the retention interval). After 3 seconds, average recall was about 80%, after 18 seconds it was about 3%. Peterson and Peterson’s findings suggested that STM duration may be about 18 seconds, unless we repeat the information over and over (i.e. verbal rehearsal).
Research on duration (Duration of STM) (Evaluation: Meaningless stimuli in STM study)
One limitation of Peterson and Peterson’s study is that the stimulus material was artificial.
The study is not completely irrelevant because we do sometimes try to remember fairly meaningless material (e.g. phone number). Even so, recalling consonant syllables does not reflect most everyday memory activities where what we are trying to remember is meaningful.
This means the study lacked external validity.
Research on duration (Duration of LTM)
Bahrick et al. (1975) studied 392 American participants aged between 17 and 74. High school yearbooks were obtained from the participants or directly from other schools. Recall was tested in various ways, including:
(1) photo-recognition test consisting of 50 photos, some from the participants’ high school yearbooks
(2) free recall test where participants recalled all the names of their graduating class.
Participants 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 accurate than recognition- about 60% after 15 years, dropping to 30% after 48 years.
This shows that LTM may last up to a lifetime for some material.
Research on duration (Duration of LTM)
(Evaluation: High external validity)
One strength of Bahrick et al.’s study is that it has high external validity.
This is because the researchers investigated meaningful memories (i.e. of people’s names and faces). When studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower (e.g. Shepard 1967).
This suggests that Bahrick et al.’s findings reflect a more ‘real’ estimate of the duration of LTM).
The multi-store model of memory: Define Multi-store model (MSM)
A representation of how memory works in terms of 3 stores called the sensory register, STM and LTM. It also describes how information is transferred from one store to another, what makes some memories last and what makes some memories disappear.
The multi-store model of memory: Define Sensory register
The memory stores for each of the 5 senses, such as vision (iconic store) and hearing (echoic store). Coding in the iconic sensory register is visual and in the echoic sensory register it is the acoustic (sounds). The capacity of sensory registers is huge (millions of receptors) and information lasts for a very short time (less than half a second).
The multi-store model of memory intro
Atkinson and Shiffrin’s MSM describes how information flows through the memory system. The model suggests that memory is made up of 3 stores linked by processing.
The multi-store model of memory: (1) Sensory register
All stimuli from the environment (e.g. the sound of someone talking) pass into the sensory register (SR). This part of memory comprises several registers (sensory memory stores), one for each of our 5 senses. Coding in each store is modality-specific (i.e. it depends on the sense). For example, the store coding for visual information is iconic memory and the store coding acoustically (i.e. for sound) is echoic memory. There are other sensory stores for touch, taste and smell information.
Duration of material in the SRs is very brief- less than half a second. The SRs have a very high capacity, for example over 100 million cells in one eye, each storing data.
Information passes further into the memory system only if you pay attention to it (so attention is the key process).
The multi-store model of memory: (2) STM
Information in STM is coded mainly acoustically and lasts about 18 seconds unless it is rehearsed, so STM is more of a temporary store. STM is a limited-capacity store, because it can only contain a certain number of ‘things’ before forgetting occurs. Capacity of STM is between 5 and 9 items of information, through Cowan’s research suggests it might be more like 5 rather than 9.
Maintenance rehearsal occurs when we repeat material to ourselves over and over again. We can keep the information in our STMs as long as we rehearse it. If we rehearse it long enough, it passes into LTM.
The multi-store model of memory: (3) LTM
This is the potentially permanent memory store for information that has been rehearsed for a prolonged time. LTMs are coded mostly semantically (i.e. in terms of meaning). Psychologists believe that its duration may be up to a lifetime. For example, Bahrick et al. (1975) found that many of their participants were able to recognise the names and faces of their school classmates almost 50 years after graduating. The capacity of LTM is thought to be practically unlimited.
According to the MSM, when we want to recall information from LTM, it has to be transferred back into STM by a process called retrieval.
The multi-store model of memory: (Evaluation: Research support)
One strength of the MSM is support from studies showing that STM and LTM are different.
For example, Baddeley found that we tend to mix up words that sound familiar when we are using our STM’s. But we mix up words that have similar meanings when we use our LTM’s. Further support comes from the studies of capacity and duration.
These studies clearly show that STM and LTM are separate and independent memory stores, as claimed by the MSM.
The multi-store model of memory: (Evaluation: Counterpoint for Research support)
Despite such apparent support, in everyday life we form memories, related to all sorts of useful things- people’s faces, their names, facts, places, etc. But many of the studies that support the MSM used none of these materials. Instead, they used digits, letters (Jacobs), and sometimes words (Baddeley). They even used what are known as consonant syllables that have no meaning (Peterson and Peterson).
This means that the MSM may not be a valid model of how memory works in our everyday lives where we have to remember much more meaningful information.