short-term memory

measuring short-term memory capacity

• Digit Span Test

• typically hold 7 (±2) items

chunking

process of “recording” information

• depends on knowledge

• powerful way to functionally increase short-term memory capacity

rehearsal

performance on short term memory tasks will be determined by

• how much people can rehearse a particular item

• how long it has to be held in memory before being recalled

Brown-Peterson Task

• prevented people from rehearsing the letters they were told to remember

• only 7% of people could recall the three letters after just a few seconds

serial position curve

• primacy effect: more opportunity to rehearse first words

• recency effect: less time for decay

proactive interference

information stored previously makes it difficult to add new information (interference from old onto new)

retroactive interference

new information coming in overwrites older information in memory (interference from new onto old)

word length effect

• reveals that memory capacity is not just a function of number of items

• word length matters because it takes longer to say long words

• short-term memory capacity varies closely with pronunciation time

• suggests that short-term memory uses sound-based representations

multiple types of representation

suggests that there might be multiple types of short-term memory stores

• results for deaf subjects showed visual confusability (R recalled in place of B)

• reveals that representations in short-term memory don’t have to be phonological (heard)

Baddeley and Hitch

short-term memory involves more than just the storage of information; info is manipulated and analyzed too

• called this memory system working memory

working memory

has multiple stores that use different forms of representation

• contains attention-like processes that control how these memory stores are used

central executive (working memory system)

• like an attentional process

• limited capacity

• gets info from sensory memory and coordinates sending info to long-term memory

• allocated info to the different stores, controls how memory is used

phonological store (working memory system)

• holds on to speech-like info

• has a silent speech process (phonological loop) that rehearses this info

  • you can’t use this process while you are talking

• capacity limited by how much can be rehearsed in a given amount of time (about 1.5 seconds)

visuo-spatial sketchpad (working memory system)

• stores mental images

• important for spatial tasks

• mean performance is ~9 filled squares on capacity tests

similarities with attention

• tasks that require the same resources will compete

• tasks that use different memory resources compete less - but all use the central executive, which also has limits