Short and Long Term Memory

Capacity

Jacobs found that the average span for digits was 9.3 items and 7.3 for letters. Miller reviewed this and concluded that the span of immediate memory was 7 +/- 2.

Evaluation

The Capacity of STM may be even more limited to about 4 chunks. Suggests that is not as extensive as first thought. Research on capacity for visual information found that 4 items was the limit.

The Size of the Chunk also matters. people have a shorter memory span for larger chunks e.g. 8 word phrases than smaller chunks.

The Capacity of STM is not the same for everyone. Recall increases with age. The age increase could be due to a gradual increase in brain capacity or that people may develop strategies to improve their memory span.

Duration

STM: Peterson and Peterson studied the duration of STM. Each pp was given a consonant syllable and a retention interval of 3, 9 or 18 seconds. On average found that they were correct 90% over 3 seconds. 20% over 9 seconds and 2% after 18 seconds.

LTM: Bahrick tested 400 people on racial recognition from a yearbook. Pp tested within 15 years of graduation are 90% accurate. after 48 years this was 70% accurate in cued recall.

Evaluation

The testing of STM was artificial. Had low ecological validity as it didn't represent everyday tasks in life.

STM results could be due to displacement. Reitman used auditory tones instead of numbers so displacement wouldn't occur and found that the duration of STM was longer. Suggests in Peterson and Peterson study forgetting was due to displacement not decay.

Coding

Baddeley found that pp had difficultly remembering acoustical similar words in STM but not LTM, whereas semantically similar words posed little problem for STM but led to muddled LTMs. This suggests that STM is encoded acoustically and LTM encoded semantically.

Evaluation

Baddeley may not have tested LTM as he only waited 20 minutes before asking for recall.

STM may not be exclusively acoustic as some experments have shown that visual codes are also used in STM.

LTM may not be exclusively semantic. Long-term recall was related to visual as well as semantic categories.

	Created by Emilia Leydon about 6 years ago

Notes on the AQA Year 1 AS Book.

Memory Notes