Coding, Capacity and Duration

Question 1

Jacob (1887)

Aim

Answer 1

To find out the capacity of STM by measuring digital span.

Question 2

Jacob (1887)

Procedure

Answer 2

• Researcher reads out 4 digits.
• Participant recalls them out loud.
• Researcher goes on to 5 digits, 6 digits, etc. until participant can no longer recall correctly.
• Indicated participant’s digital span.

Question 3

Jacobs (1887)

Digital Span

Answer 3

• Mean span for digits was 9.3 items.
• Mean span for letters was 7.3 items.

Question 4

Jacob (1887) Evaluation

Lack of Control

Answer 4

• Early research in Psychology was not very well controlled.
• Original experiment may have underestimated the digital spans because participants were distracted (confounding variable).
• However, his findings were confirmed by other, better controlled studies since (Bopp and Verhaeghen 2005).

Suggests the study was valid and has high temporal validity.

Question 5

Miller (1956)

Aim

Answer 5

Measuring span of STM and chunking.

Question 6

Miller (1956)

Procedure

Answer 6

• Made observations of everyday life.
• Noticed the repetition of the number 7 (7 deadly sins, 7 days in a week, 7 musical notes).

Question 7

Miller (1956)

STM

Short Term Memory

Answer 7

• Span of STM is 7 (±2) items.
• Noted people recall 5 words as well as 5 letters.
• Done by chunking

Question 8

Miller (1956) Evaluation

Not so many chunks

Limitation

Answer 8

• May have overestimated STM capacity.
• A review of later research showed the capacity of STM is only 4 (±2) chunks.

Suggests the lower end (5) of Miller’s estimate was more appropriate than 7.

Question 9

Peterson and Peterson (1959)

Aim

Answer 9

Duration of STM.

Question 10

Peterson and Peterson (1959)

Procedure

Answer 10

• 24 took part in 8 trials each.
• Given a consonant syllable to remember.
• Given a 3 digit number to count back from in 3s until told to stop.
• Each trial had longer counting times (3, 6, 9, 12, 15 & 18s).

Question 11

Peterson and Peterson (1959)

Findings

Answer 11

• 3 second interval gave 80% accuracy.
• 18 second interval gave 3% accuracy.

Suggests STM duration may be 18 to 30 seconds without rehearsal.

Question 12

Peterson and Peterson (1959)

Lacks ecological validity

Limitation

Answer 12

• Stimulus material was artificial.
• Recalling consonant syllables does not reflect everyday memory activities that have personal meaning.

Memory may be different when the material is meaningful.

Question 13

Bahrick (1975)

Aim

Answer 13

Duration of LTM.

Question 14

Bahrick (1975)

Procedure

Answer 14

• Studied 392 American participants between 17 and 74 years old.
• High school yearbooks were obtained from participants or their schools and proceded with 2 tests:
• Photorecognition test: shown photos and asked if the person attended their school.
• Free recall: participants recall names from their graduating class.

Question 15

Bahrick (1975)

Findings

Answer 15

• Photorecognition: participants tested within 15 years were about 90% accurate; after 48 years, recall declined to 70%.
• Free call: recall was at 60% after 15 years; dropped to 30% after 48 years.

Question 16

Bahrick (1975) Evaluation

High external validity

Strength

Answer 16

• Researchers investigated meaningful memories (ie. names and face).
• Recall rates were considerably lower on LTM studies on meaningless pictures.

Suggests Bahrick (1975) is an accurate estimate of LTM’s duration.

Question 17

Baddeley (1966a, 1966b)

Aim

Answer 17

How information is coded in different memory stores.

Question 18

Baddeley (1966a, 1966b)

Procedure

Answer 18

Gave different word lists to 4 groups of participants to remember:
- Group 1: acoustically similar;
- Group 2: acoustically dissimilar;
- Group 3: semantically similar;
- Group 4: semantically dissimilar.

Question 19

Baddeley (1975)

Findings

Answer 19

When asked to recall the correct order of the words:
- STM: worse on acoustically similar words;
- LTM: worse on semantically similar words.

Question 20

Baddeley (1975) Evaluation

Separate memory stores

Strength

Answer 20

• Identified a clear difference between two memory stores.
• Later research proved the idea that STM used acoustic and LTM uses semantic has temporal validity.
• Important for understanding memory.
• Led to the MSM.

The study was important to understanding memory and led to the development of the MSM.

Question 21

Baddeley (1975) Evaluation

Artificial Stimuli

Limitation

Answer 21

• Word lists had no personal meaning to the participants.
• Baddeley’s findings may not tell us much about coding in meaningful, everyday tasks.
• For meaningful information, semantic coding may be used for STM.

Suggests findings have limited application.