1. Coding, Capacity and Duration of memory (●'◡'●)

what is the STM?

the limited capacity store. in stm, coding is mainly acoustic (sounds), capacity is between 5-9 items on average, duration is around 18 seconds.

what is the LTM?

The permanent memory store. in LTM, coding is mainly semantic (meaning), it has unlimited capacity and ca store memories for up to a lifetime.

define coding

the process of converting information into different forms

Describe the research Alan Baddeley conducted on coding.

Baddeley (1966) gave different lists of words to four groups of pps to remember.

group 1: acoustically similar words

group 2: acoustically dissimilar words

group 3: semantically similar words

group 4: semantically dissimilar words

pps were then shown the original words and were asked to recall them in the correct order.

when they did this immediately, recalling from short term memory, 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.

What is the definition of capacity?

capacity refers to the amount of information that can be held in a memory store at one time. In short-term memory (STM), it is typically between 5 to 9 items, while in long-term memory (LTM), it is considered unlimited.

what was the first experiment on capacity (Joseph Jacobs 1887)

The Digit Span test.

a researcher reads out four digits and the participant recalls them out loud in the correct order. if this is correct, the researcher reads out five 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, and the mean span for letters was 7.3.

Second experiment on capacity? (George miller 1956)

Miller’s Magic Seven.

• he made observations out of everyday practice. e.g. 7 notes on a musical scale, 7 deadly sins, 7 days of the week etc….

• miller though that this was no accident - the span (i.e. capacity) of STM might be about 7 (+2/-2).

• he also noted that people can recall five words as easily as they can recall five letters. We do this by chunking - grouping sets of digits or letters into units or chunks.

What is the definition of duration of memory?

the length of time information can be held in memory

Describe the experiment Peterson and Peterson conducted on the duration of memory.

Peterson and Peterson (1959)

• tested 24 students in eight trials each (trials=test)

• on each trial, the student was given a consonant syllable (e.g. YGC) to remember

• they were also given a three digit number. (both of the triagrams and the numbers were meaningless)

• the student then counted backwards from this number until told to stop.

• the counting down backwards was to prevent any mental rehearsal of the consonant syllable (which would increase the duration of STM memory for the 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 around 3%

• these findings suggest that STM duration may be around 18 seconds, unless we repeat the information over and over again (i.e. verbal rehearsal)

Describe the experiment Bahrick et al. conducted on the duration of memory.

Harry Bahrick et al. (1975)

• studied 392 American participants, aged between 17 and 74.

• high school yearbooks were obtained from the participants directly or from some 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.

Evaluate Baddeley’s research into coding.

SEPERATE MEMORY STORES. ✅

-it identified a clear difference between the two memory stores.

-important step in our understanding of the multi-store model.

ARTIFICIAL STIMULI. ❌

• used quite artificial stimuli rather than meaningful material

• the word lists has no personal meaning to the participants, so his findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life.

• when processing information, people may even use semantic coding for STM tasks. this suggests the findings have limited application.

Evaluate capacity (hint: using the two studies by Miller and Jacobs)

A VALID STUDY✅ (jacobs)

• it has been replicated many times

• this study is an old one and early research in psychology lacked many adequate controls. For example, some participants’ digit spans might have been underestimated because they were distracted during testing (an extraneous variable) despite this, jacobs’ findings have been confrimed by other, better controlled studies since.

This suggests that Jacobs’ study is a valid test of digit span in STM.

NOT SO MANY CHUNKS ❌ (miller)

• Miller may have overestimated STM capacity.

• Nelson cowan (2001) reviewed other research and concluded that the capacity of STM is only 4 (plus or minus 1) chunks.

This suggests that the lower end of Miller’s estimate is more appropriate than seven items.

Evaluate duration (hint: using the two studies by Peterson and Bahrick)

DECAY VS INTERFERENCE❌

• results may be due to interference, not decay.

• Peterson and Peterson concluded that the forgetting in STM was due to the decay or memory traces over time.

• However, it could also be due to the interference from counting backwards.

This suggests that the conclusions about duration of STM may not be valid.

HIGH EXTERNAL VALIDITY✅

• this is because the researchers investigated meaningful memories (i.e. peoples’ names and faces). When studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower.

This suggests that Bahrick et al.’s findings reflect a more ‘real’ estimate of the duration of LTM.