Magical number 7 - miller’s article
- we can hold only a limited number of items/chunks of information in the STM (7±2)
- chunk: memory unit of several components that are strongly associated with one another.
- behaviorism: emphasis on observable external events.
STM capacity limits: brown/Peterson and Peterson technique
- task: presented with items they should remember, distracting task to prevent rehearsal and recall task.
- materials stored for less than 1 minute is frequently forgotten
STM capacity limits: serial position effect
- U shaped relationship between word’s position in a list and its probability of recall.
- recency effect: better recall for items at the end of the list.
- primacy effect: better recall for items at the beginning of the list.
STM capacity limits: semantic similarity
- experiment wiht digits and words
- pro-active interference (PI): trouble learning new material due to interference of old material. Release can be done via semantic change.
- retro-active interference (RI): past learning is forgotten and you can remember new knowledge easily.
- semantic factors influence number of items that can be stored.
- degree of semantic similarity is related to the amount of interference
Working memory: overview
- baddeley and hitch 1974
Components:
1. Central executive - attentional system
2. Phonological loop - speech processing
3. Visuospatial sketchpad - visual processing
4. Episodic buffer - temporary storage for integrated information
- all components have limited capacity and function independently
Assumptions:
1. Multitasking (duality): two tasks use the same component, they cannot be performed successfully
2. Multitasking (uni-model): two tasks use different components, can perform successfully.
Working memory: phonological loop
- passive: speech perception
- articulatory: speech production (rehearsal)
- phonological similarity effect: reduced immediate recall when words are similar, unsure if its because of acoustic similarity (sounds) or articulatory similarity (articulatory movements).
- word length effect: word span is greater for short words.
Working memory: visuospatial sketchpad
- visual processing: what and left hemisphere
- spatial processing: where and right hemisphere
- visual cache: visual form and color
- inner scribe: spatial and movement and involved in rehearsal.
Working memory: evaluation of visuospatial sketchpad
much remains unknown:
- seperatedness of the visual and spatial component
- interaction between visuospatial sketchpad and episodic buffer
- rehearsal processes within the visuospatial sketchpad.
Working memory: central executive
- attentional system, most important and versatile.
- involved in complex cognitive activities but does not store information.
- prefrontal cortex is most active
- 4 processes: focusing attention, dividing attention between stimulus streams, switching attention between tasks and interfacing with LTM.
Working memory: miyake et al’s executive functions (theoretical approach)
To identify the number and nature of executive processes. 3 executive processes: inhibition, shifting and updating.
1. Updating = common EF + updating specific abilities
2. Shifting = common EF + shifting specific abilities
3. Inhibition = common EF
the unity/diversity framework:
- each excutive function consists of whats common to all three + whats unique
- Common EF: one’s ability to actively maintain task goals and goal-related information and use this information to effectively bias lower-level processing.
- diversity evidence: each executive function had a specific brain area + a common brain area (left lateral pre-frontal cortex).
Working memory: dys-executive syndrome
- impaired central executive
- impaired response inhibition, rule deduction and generation, maintainance and shifting of sets etc.
- flawed model: each executive process is associated with a different region within the frontal cortex so the syndrome affects everyone differently.
Working memory: central executive evaluation
- based on both behavioral and neuro-imaging evidence
- dys-executive syndrome is misleading
- limitations: task-impurity problem (hard to identify the contribution made by any specific executive process), number and nature remains unclear.
Working memory: episodic buffer
- holds integrated information about episodes or events in a multi-dimensional code combining visual, auditory and other sources of information.
- buffer between other components of the memory system
- links WM to perception and LTM
- capacity is approximately 4 chunks
Working memory: episodic buffer evaluation
- storage facility
- passive structure
- limitations: separate inputs (unclear how information is combined), research on other sensory modality is lacking (smell and taste).
Working memory: overall evaluation
Maxis-pans article: abstract
- Hypothesis: the capacity of verbal WM is > 4 (8)
- Assumption: two systems involved (phonological loop and central attentional system (episodic buffer and executive loop)
- Aim: get participants to use both systems effectively to increase the capacity from 4 to 8.
Maxis-pan article: procedure
- first repeat a limited number of blue letters (up to 4) out loud (phonological loop) and then remember the rest of the black letters (up to 6) in their heads (central attentional system).
Simple spans article: results
- better performance on maxis-pan
- memorize x-number of blue letters and many black = simples-pan: fewer blue letter, maxis-pan: no visible effect
- memorize 3 or fewer blue letters and x-number of black = simples-pan: recency/primacy effect
- memorize 3 or more blue letters and x-number of black = maxis-pan: recency/primacy effect (phonological loop is overloaded)
Simple spans article: conclusion
- number of black letters has no influence on the number of blue letters in the maxis-pan = two independent systems used.
- maxis-pan leads to remembering more units
