Memory

Jacobs - Capacity experiment: Jacobs gave participants a series of either digits/letters and asked them to repeat them He then added more digits/letters until the participant couldn't repeat them accurately He found that people could remember between 5 and 7 letters and up to 9 digits Lacks ecological validity - people don't often have to remember a series of letters/digits There may have been other confounding variables Chunking: Miller made observations of everyday practice He noted that things come in 7s - 7 notes on a music scale, 7 days of the week etc. This suggests that the span of STM is about 7 items (plus or minus 2) Miller also noted that people can recall 5 words as well as they can recall 5 letters. They do this by chunking - grouping sets of digits or letters into units or chunks

Peterson & Peterson - STM Duration experiment: 24 undergrads were given trigrams (a group of 3 consonants) to remember. They were also given a 3 digit number They were asked to count backwards from the 3 digit number. This was to prevent any mental rehearsal of the trigram On each trial they were told to stop after a different amount of time - 3, 6, 9, 12, 15, and 18 seconds. This is called the retention interval After 3 seconds 80% were remembered correctly After 18 seconds only 10% were remembered correctly This shows STM has a very short duration Lacks ecological validity

Bahrick - LTM Duration experiment: Studied 392 participants from Ohio, aged between 17 and 74 High school yearbooks were obtained from the participants or directly from schools Recall was tested in various ways including; a photo recognition test consisting of 50 photos, some from the school yearbooks, and a free recall test where participants recalled the names of their graduation class Participants who were tested within 15 years of graduation were about 90% accurate in photo recognition and 60% accurate in free recall Participants who were tested within 48 years of graduation were about 70% accurate in photo recognition and 30% accurate in free recall This shows LTM can last a very long time High external validity - uses real life meaningful memories Confounding variables were not controlled - participants may have looked at book and rehearsed memory over the years

Baddeley - Coding experiment: He gave students a number of words that were split into four groups; acoustically similar, acoustically dissimilar, semantically similar and semantically dissimilar He then asked them to repeat them immediately or after 20 minutes When asked to repeat them immediately, participants did worse with acoustically similar words showing STM is coded acoustically When asked to repeat them after 20 minutes, participants did worse with semantically similar words, showing LTM is coded semantically Used artificial material - the words had no meaning to the participants. When processing more meaningful information, people may use semantic coding even for STM tasks