Coding, Capacity and Duration of Memory

Short-Term Memory: The limited-capacity memory store. Coding is mainly acoustic, capacity is 7+/-2 chunks of information and duration is 18 seconds.

Long-Term Memory: The permanent memory store. Coding is mainly semantic, it has an unlimited capacity and can store memories for up to a lifetime.

Coding: The format in which information is stored

Capacity: The amount of information that can be held in a memory store

Duration: The length of time information can be held in memory

Alan Baddeley (1966): Participants were given 1 of 4 word lists, acoustically (dis) similar or semantically (dis) similar. Participants either recalled the list immediately or after a delay. When recalled immediately the acoustically similar words were remembered worst, semantically similar words were remembered worst when recalled after 20 minutes

Separate Memory Stores: Baddeley’s study showed distinction between two memory stores. The idea that the STM uses acoustic coding and the LTM uses semantic coding is continually supported.

Artificial Stimuli (Baddeley’s Research): The word lists had no personal meaning to participants so Baddeley’s research may not tell us much about coding in different kinds of memory tasks.

Joseph Jacobs (1887): Participants saw increasingly long lists of numbers or letters and had to recall them in the right order. Two-syllable letters or numbers were left out. The capacity for numbers was 9, and for letters, it was 7.

George Miller (1956): Observed everyday practise and showed that the span of information held within STM is 7 items but that, through chunking, the capacity can be increased.

Replication of Jacobs Study: Jacobs findings have neen confirmed by other, better controlled studies, such as Bopp and Verhaeghen (2005).

Miller Overestimation: Miller may have overestimated the STM capacity. Nelson Cowan (2001) reviewed other research and concluded actual capacity of the STM was 4+/-1 chunks.

Peterson and Peterson (1959): Tested 24 students in 8 trials each and on each trial, they were given a consonant syllable to remember and then they had to count back aloud from a 3-digit number for either 3, 6, 9, 12, 15 or 18 seconds and then recall the syllable. After 3 seconds, average recall was 80% and after 18, it was 3%.

Bahrick et al (1975): This study asked participants to recall students from their high school by name or by face. It found that memory aided by a photo was 90% accurate after 15 years and 70% after 48, but free recall of names or faces led to 60% accuracy after 15 years and 30% after 48.

Artificial Stimulus of Research (Peterson and Peterson): Recalling consonant syllables doesn’t reflect most everyday memory activities where what we are trying to remember is meaningless, the study lacks external validity.

Bahrick’s High External Validity: The researchers investigated meaningful memories and when studies on the LTM were conducted with meaningless pictures to be remembered, recall rates were lower.