STM, LTM, and Working Memory

66 - 74

First studies on memory were

around 1885

First studies of memory used … as a participant

Ebbinghaus (used himself)

Ebbinghaus used lists of

CVC trigrams

• meaningless consonant-vowel-constonant syllables

• DAX, YAT, etc

Describe the early study of forgetting

• how memories of deteriorated with time

• index of retention:

  • trials to learn minus trials to fully re-learn (e.g. 20-15=5)

  • express value as a percentage of original trials (e.g. 5/20=25%)

Explain the forgetting curve

• sharpest decline in memory in the first 20 minutes

• fast decay continues through the first hour

• the curve begins to completely level off at an hour

• the curve levels off after about one day

What does the pattern of the forgetting curve suggest

suggests the existence of short-term and long-term memories that are differentially sensitive to forgetting

Memory is formed from three linked storage sub-systems

• sensory memory

• short-term memory

• long-term memory

  • the duration of memories, and the storage capacity of the sub-systems increases from left to right (in this top to bottom)

What is sensory memory

• Stimuli in the environment that are detected are initially encoded in sensory memory

• Iconic = visual

• Echoic = auditory

• Haptic = touch

What is short term memory store

• Information that is attended to in the sensory register enters short-term memory

• Rehearsal of information increases duration of short-term memory and the likelihood that information will be transferred to long-term memory

• Information from the long-term store can be retrieved to help with current decisions in order to generate behavioural responses

What is long term memory

• A ‘permanent’ memory store

• Information can only get into long term memory if it is rehearsed in short term memory

Research on the sensory store originally focussed on

iconic (visual) memory, it was originally thought that the sensory store had a very limited duration and storage capacity

Describe the study to see the capacity and duration of iconic memory

• Brief presentations of a visual pattern (5-500 msec)

• Participants were then required to recall the letters presented in a particular trial (total report)

• Performance on this task was poor

  • Participants were able to recall about 4 letters (33%)

  • But many couldn’t remember past the first line of letters in the display

• Concluded that iconic memory as very limited in terms of capacity and duration

  • Only a few elements are retained for a very short period of time

What is the primary effect in memory

remember most of the first items on the list, depends on the rehearsal of the first times in STM

What is the recency effect in memory

remember most of the last items on the list, transfers items to LTM

STM has a capacity of

limited capacity, 7 items

Atkinson and Shiffrin’s model contained a

unitary short term memory store with limited capacity and duration

If it is a unitary store, any kind of info processed in STM should cause

interference – we should not be able to multi-task

Describe Baddeley & Hitch (1974) study

• 2 groups of participants

• Some participants had to memorise a list of words presented sequentially

• Other has to memorise a list of words while counting backwards

• The number of words recalled by the participants was similar in both the single and dual task groups

• Participants performed similarly despite the supposed limited capacity of the short-term store in Atkinson and Shiffrin’s model

• These results suggest that short-term memory must be broken down into separate components

The phonological loop holds

speech-based information for about 2 seconds

How can information be maintained

by subvocalised rehearsal (repetition of information)

The visuo-spatial sketchpad encodes

visual material, and information relating to space

The task of the central executive is to

input from other sub-systems to control our actions/behaviour

The central executive is integrated into a set of systems to

focus/divide attention, generate recall of information from LTM via the episodic buffer

Who introduced the episodic buffer

Baddeley (2000)

What is the episodic buffer

a temporary store of limited capacity, where visual, language, and LTM information can be combined

2 verbal tasks is an example of interference in the

phonological loop

2 spatial tasks is an interference in the

sketchpad

Long term memories are broken down into three distinct categories

• episodic

• semantic

• procedural

What is episodic memory

for personal events that happened in the past

• allows us to remember what, where, when things happened

• usually the kind of memory we fail to retrieve from our early childhood, e.g. first swimming lesson

What is semantic memory

abstract knowledge about the world

• names of things, people, places

• e.g. what a swimming pool is

What is procedural memory

memory for how to do things

• riding a bike, brushing teeth, swimming

STM capable of holding around … for …

5 - 7 items for 15-30 seconds

What is implicit memory

• remembered ‘without thinking’ and hard to verbalise

• unconscious or automatic memory

• procedural memories: skills and tasks, e.g. how to ride a bike

What is explicit memory

• conscious or deliberate memory

• after ‘thinking’ you can verbalise what you remember

• declarative memories: facts, figures, and events

  • split into episodic and semantic memory

  • episodic memories are different between people because we have different experiences