Psychology Memory

LTM - Unlimited                                                STM - measured in seconds

Shepard 1967: tested duration of LTM. Showed Paricipants 612 memorable pictures one at a time, an hour later they were shown some of the pictures among a set of others. This showed almost perfect recognition. Four months later they were still able to recognise 50% of the photos.

Peterson and Peterson 1959: tesed duration of STM. 24 participants were asked to recall a nonsense trigram that had no meaning, immediately after hearing it they had to count backwards in 3s or 4s to make sure they did not rehearse it. Each participant was then given trials. On each trial the time spent couning backwards was different, participants remembered about 90% when there was only a 3 second interval, and about 2% when there was an 18 second interval.  This suggests that STM lasts about 20 seconds.

Validity: They only studied one type of memory- syllables and words

             :They were not testing duration as when they couted backwards the nonsense syllable could've been displaced in STM, so wiping out the memory.

LTM - unlimited                                           STM -less than 7 chunks

Miller 1956 : found the magic number, 7 plus or minus 2, he also found that people can recall 5 words as well as they can recall 5 letters - we call this "chunking".  However the size of the chunk matters

Simon 1974 : found that people had a shorter memory span for large chunks such as 8 word phrases than smaller chunks such as one syllable chunks

Cowan 2001 : reviewed a variety of studies on the capacity on STM and concluded that STM is likely to be limited to 4 chunks.

Individual Differences - Jacobs found that digit span can increase with age.

Applications - Postcodes ie BS for Bristol

LTM - semantic

STM - acoustic or visual

Baddeley 1966 : tested the effec of acoustic and semantic similariy on shrot and long term recall. He found that acoustic similarity decreases STM recakk and semanic similarity decreases LTM recall.

Brandimote 1992 : found that participants used visual encoding in STM if they were given a visual task and prevented from using verbal rehearsing.

Frost 1972 : showed that long term recall was related to visual as well as semantic categories.  

The MSM is an explanation of how memory processes work

First described by Atkinson and Shriffin in 1968

The Sensory Store: Sperling 1960-  gave evidence for sensory store, participants saw a grid of letters and digits for 50 milliseconds. When asked to report the whole thing, their recall was poorer than when asked to recall one row only. This shows tha information decays rapidly in thesensory store

The Serial Position Effect: Glanzer and Cunitz 1966-  when participants were presented with a row of 20 words or shown the words one at a time, they tended to remember the first and last words. This is called the primacy and recency effect. The primacy effect occurs because the firs words are better rehearsed, The recency effect occurs because these words are still in STM when you start recalling the list.

Areas of the brain associated with STM and LTM: Beardsley 1997- Using PET scans, beardsley found that different parts of the brain were active when using STM or LTM. Prefrontal cortex- STM, Hippocampus -LTM.

Case Studies: HM- brain damage from trying to remove the hippocampus to reduce his epilepsy. His intellect remained the same but he could not form any new long term memories but he could remember things from before surgery.