Memory - coding, capacity and duration

What is coding

The process of converting info between different forms

Baddeley’s procedure

Gave different lists of words to 4 groups of participants: acoustically similar (sound similar), acoustically dissimilar, semantically similar (meaning similar), and semantically dissimilar.

Participants then asked to recall words in correct order.

Baddeley’s findings

Participants had difficulty recalling acoustically similar words in the short term, while semantic similarities affected recall in the long term. This illustrates the importance of coding in memory.

What is capacity?

The amount of info the STM can hold at one time

Jacob’s research into digit span

Researcher reads 4 digits and increases the number until the participant can no longer recall them accurately. Final number = digit span.

Jacob’s findings

Mean span for digits = 9.3, mean span for letters 7.3

Miller’s research

Everything comes in 7’s e.g. musical scale, days of week, deadly sins. So the capacity of STM is 7 items ± 2

Chunking

Grouping sets of digits or letters so they are easier to recall

Duration of STM

Peterson and Peterson tested 24 students in recalling trigrams after varying delays, finding that duration is limited to about 18 seconds unless we repeat the info over and over.

Duration of LTM

Bahrick studied 392 American participants, tested them with photo recognition test and free recall test.

Photo recognition - 90% accurate after 15 years, declined to 70% after 48 years.

Free recall - 60%. after 15 years, 30% after 48 years.

Strength of coding

Identified a clear difference between 2 memory stores, despite some exceptions, the idea STM is mostly acoustic coding and LTM is semantic has stood test of time. Eventually led us to the multi-store model.

Limitation of coding

Artificial stimuli used rather than meaningful material, the list of words had no personal meaning to participants so the findings don’t generalise to everyday life, When processing meaningful info we may use semantic even for STM. Limited application.

Strength of capacity

Jacob’s study has been replicated. Original study lacked adequate controls so suffered confounding variables, but has been replicated and confirmed. Gives study validity.

Limitation of capacity

Millers research may have overestimated STM capacity. A review concluded capacity was only about 4. Lower end of Millers estimate more appropriate.

Limitation of duration

Peterson and Peterson used artificial and arbitrary stimulus material. Doesn’t generalise to everyday life. Study lacks external validity.

Strength of duration

Bahrick’s study has high external validity because researchers investigated meaningful memories (peoples names and faces). When lab studies have been done with meaningless photos recall rates were lower. So Bahrick gives more meaningful estimate.