week 3 - short term memory

components of short term memory

retention of a small amount of memory for a brief period (15-30 seconds), not involved in manipulating stored information

typical STM study paradigm

study/encoding phase → retention interval (IV) → test phase (DV)

Retention interval in study paradigm

different stimuli, more or less stimuli, shorter or longer retention

digit span

the length at which a participant correctly recalls the sequence in the correct order on 50% of the occassions

what is the normal range of digit span

7 plus or minus 2 (Miller)

chunk

each individual unit, chunking into 3 groups of three is ideal

Articulatory loop

the active rehearsal component; maintains the information (inner voice)

The phonological store

has a limited capacity that is refreshed or maintained by the articulatory loop

The Phonological Similarity Effect

The numbers of errors during retrieval increases with sets of similar sounding (rather than looking) items

Articulatory suppression and word recall

Significantly reduces recall, subvocal repetition of non-related words (i.e. ”the”) interferes with articulatory encoding AND rehearsal

Semantic similarity effect on recall

Has no effect on recall, Semantic similarity impairs recall when a longer delay is introduced

Word Length Effect

Verbal STM is negatively correlated to the number of syllables in test words

Phonetically large items decay before they can be refreshed by articulatory rehearsal

Should You Listen to Music While Studying

Sounds that are highly dynamic tend to be more disruptive to STM (no other sounds that are interfering with loop)

Individuals with a greater memory span are more susceptible to irrelevant sounds

The rehearsal processes someone with a greater memory span

advanced and depend on silence

Separate mechanisms interact with the phonological loop to maintain serial order during retrieval

context and primacy

Changing Context

Each chunk is associated with a context, which fluctuates over time (time itself as a context)

Primacy

The first chunk is encoded with the most activity → each subsequent chunk receives less activity

Receny Effect

Attributed to STM, more recents items recalled better, still present in short-term store, affected by delay and distractions

Primacy Effect

 Attributed to LTM, more opportunity for rehearsal, affected by how many variables know to impact LTM

the Change-Detection Task (Visuospatial)

Arrays of squares can be altered in either colour or position

Participants are tasked with determining if a change has occurred following a brief delay

Articulatory suppression required

Visual STM seems to have a capacity of 3-4

The Limits of Visuospatial STM can be observed using EEG

EEG used to track precise temporal patterns of cortical activity during vSTM tasks Stimulus presentation was correlated with a spike in activity 200ms following presentation

This spike would maintain until the stimulus was tested (active rehearsal)

Visual test stimuli can be broken down into two sensory dimensions

shape and colour 

The Capacity of Visuospatial STM is Dependent Both on The Number or Stimuli and Their complexity

Information held in vSTM seems to have a finite limit (about 4-5) with the complexity of the information mediating this limit

Brain Injury Studies Suggest that Verbal and Visuospatial STM may be separate neural processes

Some patients have global STM deficits

Other cases exist with intact phonetic STM and impaired visuospatial STM and vice versa

What is the significance of articulatory suppression inhibiting the word length effect in the context of verbal STM?

Verbal short memory exists as a auditory cope, it supports the phonological loop hypothesis. If you can not repeat the word to yourself and that tanks performance - your verbal memory is dependent on a auditory code that is refreshed by rehersal