Capacity of STM - Jacobs (1887)

Question 1

Aim

Answer 1

To examine how much information the STM can hold at a given time.

Question 2

Procedure

Answer 2

• Laboratory experiment.
• Sample of 443 females aged between 8-19 years.
• Participants told to repeat a string of numbers or letters increasing in length until they couldn’t recall the sequence.

Question 3

Findings

Answer 3

• Average span of 5-9 items.

Question 4

Conclusion

Answer 4

• Capacity of STM is 7+/-2 chunks of information.
• Our STM stores chunks of information.

Question 5

Strength

Answer 5

• Laboratory experiment and therefore very controlled.
• Extraneous variables were controlled.
• For instance, an extraneous variable would have been the pace at which the letters/digits were read out. It would have been unfair if they were read quickly to some participants then slowly to others.
• To control this extraneous variable, a metronome was used to ensure they were all read at the same pace.
• Increases the reliability of the experiment.

Question 6

Weakness

Answer 6

• Lacks ecological validity due to artificial nature of the experiment.
• People don’t tend to recall strings of letters or numbers in everyday life (unless they are trying to remember a phone number, for example).

Question 7

Weakness

Answer 7

• Lacks population validity.
• Although a large sample of 443 females were used, their age range was very narrow (8-19 years).
• Therefore we cannot apply the findings of this experiment to other age categories, such as an older population.