WM 2 - capacity and variation

Question 1

key concepts

Answer 1

• activation-based models
• working memory capacity
• variation in working memory

Question 2

Miller’s magical number 7

Answer 2

• short term memory
• when asked to remember digits or letters in a (random) sequence
• Ps on average get 7 +/- 2 correct

Question 2

ways to boost short term memory capacity

Answer 2

• active rehearsal
  –> continuously saying the first parts of the sequence and adding a new digit/letter each time
• chunking
  –> splitting the sequence into smaller and more memorable chunks
  –> e.g. spotting ‘OMG’ or ‘WTF’ in the letters

Question 3

Cowan’s magical number 4

Answer 3

• only representations in the focus of attention are available to conscious awareness and report
• on average, the capacity limit of adults’ focus of attention is 4 +/- 1 information elements

Question 4

set-size effect - typical findings

Answer 4

• works for simple span and complex span (remember letter and decide if equation is correct - memory + processing)
• larger set sizes make both simple span and complex span performance worse

Question 5

three hypotheses that limit working memory

Answer 5

1. decay
2. interference
3. limited resource

Question 6

decay hypothesis

Answer 6

• working memory representations rapidly decay over time (they get weaker, we see primacy and recency effects)
• rehearsal prevents forgetting
• working memory capacity is how much information can be restored
  –> restoration mechanisms:
  1. rehearsal: subvocally repeat memoranda to maintain them
  2. refreshing: think of memoranda to keep memory traces active
• the passage of time causes nothing by itself (time is correlated with processes that cause forgetting)

Question 7

interference hypothesis

Answer 7

• working memory is limited by mutual interference between representations
  –> types of interference:
  1. confusion
  –> similar but different, slight overlap
  2. superposition
  –> increasing dissimilarity decreases performance
  3. overwriting
  –> things that sound similar, could override each other

Question 8

resource hypothesis

Answer 8

• working memory capacity is determined by a limited quantity of resource that enables holding representations available

Question 9

resource models

Answer 9

• a resource is a limited quantity that enables a cognitive function or process, such that its probability of success increases the larger the amount of resource assigned to it
• two types of models:
  1. slot models
  2. flexible-resource models

Question 10

slot models (resource model)

Answer 10

• resources are distributed in discrete units (defining the number of items one can store)
• quality of the retained representations is not perfect, but sufficiently high
  –> e.g. the egg box metaphor

Question 11

flexible-resource models (resource models)

Answer 11

• resources are distributed flexibly
• allowing for:
  1. a small number of high quality objects
  OR
  2. a high number of low quality objects
  –> e.g. the memory drive metaphor

Question 12

how is the resource allocated to representations?

Answer 12

• discrete = allocation of resource to a limited number of items, with no information stored about additional items
• continuous = equal spread of resource among all items, with fewer resource per item for larger arrays

Question 13

which hypothesis for limited STM capacity is the best?

Answer 13

• as of now, no hypothesis can explain all of the findings out there
• resource model is most suitable but still has limitations

Question 14

variation in working memory

Answer 14

• people differ in their working memory capacity
• capacity is greater in:
  –> older children than younger children
  –> younger adults than older adults
  –> healthy people than people with frontal-lobe damage
  –> some younger adults than other younger adults

Question 15

why is it important to understand the variation in working memory capacity?

Answer 15

• correlates with complex cognitive activities:
  –> reading comprehension
  –> reasoning
  –> problem solving
• predicts:
  –> cognitive development
  –> individual differences in intellectual abilities

Question 16

why do people differ in working memory?

Answer 16

• examine commonalities between working memory performance and other abilities
  –> e.g. a working memory task and a reasoning task

Question 17

proposed explanations for why people differ in working memory?

Answer 17

1. executive attention hypothesis
2. building hypothesis

Question 18

the executive attention hypothesis

Answer 18

• a single top-down executive attention system underlies both working memory and reasoning task performance:
  –> executive attention impacted by:
  –> disengagement & maintenance
  –> impacts task performance
• two systems:
  1. one is quick and simple
  2. one is controlled and involves effortful processing (attention controlled system)

Question 19

executive attention in a working memory task

Answer 19

• maintain access to relevant information and append new information to the list
• disengage from and suppress outdated information from previous trials

Question 20

executive attention in a reasoning task

Answer 20

• maintain problem and allow systematic hypothesis testing
• disengage from outdated hypotheses and prevent returning to them

Question 21

summarise executive attention hypothesis

Answer 21

• working memory capacity and reasoning ability are two sides of the same coin
  –> both arise from limited executive attention
• people with better executive attention will perform better in working memory, reasoning, and other similar tasks

Question 22

what is the problem with the executive attention hypothesis?

Answer 22

executive attention tasks do not correlate well, so it is difficult to directly test this hypothesis

Question 23

the binding hypothesis (why people differ in WM)

Answer 23

• a system for rapid formation of temporary bindings underlies both working memory and reasoning task performance
• binding = construction and manipulation of representations of novel structures

Question 24

binding hypothesis details

Answer 24

• bindings are temporary links of content representations to places in a mental coordinate system
• the working memory capacity limit is the number of bindings maintained; it arises from interference between bindings
• people who suffer less interference can build more complex structural representations
• therefore, they will perform better in working memory, reasoning, and other similar tasks

Question 25

problem with the hypothesis

Answer 25

• bindings may be constructed and maintained with the help of executive attention, making it difficult to directly test this hypothesis against the executive attention hypothesis
• more research is needed to answer the question why people differ in working memory capacity

Question 26

summary

Answer 26

• activation-based models assume that working memory holds information temporarily in a heightened state of availability
• limits of working memory capacity have been hypothesised to arise from decay, interference, or resource
• variation in working memory can be measured with latent-variable modelling
  –> it is a matter of debate whether it is caused by individual differences in executive attention or the number of bindings