Short-Term Memory

History

William James - 1890, father of two-part memory system

  • Primary memory - memories that never leave consciousness, part of the psychological present

  • Secondary memory - a memory absent from the consciousness and belongs in the psychological past

Short-term memory - memory that is limited in duration and capacity

Long-term memory - typically any memory more than a few minutes old; can last a few minutes to a lifetime

Atkinson and Schiffrin (1968) - multistore system of memory; the “modal” model of memory

  • Proposed there are separate short-term and long-term memory stores

Baddeley and Hitch (1974) - proposed the evolution of a single short-term memory into working memory

Short-Term Memory Tasks

Distractor task - attempts to quantify the duration of immediate memory over brief delay intervals while rehearsal is prevented

  • Do something opposite that interrupts cognitive process, checks to see how much we can interrupt potential short-term input

  • We find that short-term memory can be highly manipulable

  • By and large, outlines what happens to us on a daily basis when we’re studying, learning, engaging

Brown-Peterson task - items are presented for retention, usually three letters or words; typically, items can be recalled accurately if tested immediately

Caveat to distract task: What happens if the lapse in memory is due not to memory loss but due to interference from earlier trials?

  • Proactive interference - items presented on earlier trials interfere with recall of the current list of to-be-remembered items

  • Items with similarity to the to-be-remembered can also interfere with memory

Forgetting occurs more rapidly across trials; however, shifting the category of the target items can dramatically increase recall, a phenomenon called release from proactive interference

  • If we’re showing pictures of faces then switch to pictures of buildings, it violates proactive interference

  • If you study the same material for a long time, it can start to morph and create poor understanding (why cramming doesn’t work)

Memory Span

Second measure of STM is related to its capacity

Memory Span - the longest sequence of items that can be remembered in correct order after a single presentation

  • Recall is immediate; without delay or distractor

  • Often consists of five to nine items (think plus/minus 7 rule) that can be recalled correctly

World-length effect - more items can be remembered when short words are the to-be-remembered items

Characteristics of Verbal Short-Term Memory

Recent memories (STM) are rich in sensory quality such as color, sound, and texture

  • Objective features have been attributed to STM:

  • Acoustic encoding

  • Limited capacity

  • Limited duration

  • Susceptibility to forgetting

  • Transfer to long-term memory

  • Control Processes

Acoustic Encoding - It is what is “sounds like”; words are remembered as they sound as though they are being verbally rehearsed

  • LTM usually remembers the meaning of a word via semantic encoding

  • We remember meaning rather than sound

Man, Can, Mad, Cap, Map - all sound similar and can be confused, but when encoded and recalled by meaning, the words are more easily remembered

  • Man is not the same as ball cap, it is not the same a map, etc.

Verbal-semantic encoding - instantaneous recall of a phrase is close to verbatim, later recall is done in paraphrases

Limited Capacity & Duration - The average person can remember seven items in a memory span test

  • This doesn’t mean the STM is only seven items

What is an “item”?

  • A letter, word, idea, picture, etc.

  • Items are proposed as a unity already existing in LTM

Memory span can be enlarged by increasing the amount of information within each item.

Chunking - the parsing and encoding of material in meaningful units

Forgetting

STM is sensitive to disruption

  • Forgetting from STM is due to displacement of old items by new items

  • The capacity limit means the addition of new items requires dropping some items already in STM

STM retention often takes place in the context of divided attention

  • More interference occurs if speech is in the background as compared to white noise

Transfer to LTM

STM functions as a mode to transfer info into the LTM

Maintenance occurring in the STM is the process of rehearsing, forming images, or mnemonics to aid the development of permanent memories of information

  • Caveat: STM is not required for LTM development

Individuals with brain injuries can still learn and encode memories into their LTM

  • KF had a poor STM but a high functioning LTM

  • Inverse: HM had a good STM but could not encode new memories into LTM

Control Processes

Humans can, to a degree, control how to STM

  • Control where to direct attention

  • How to code new inputs

  • When to rehease

  • Which retrieval cues to use

Control processes define the STM as an active rather than passive information store

Other Modalities of STM

Visual STM - images are presented, participants are asked to recognize if the picture is known or unknown

Spatial STM - spatial positions are shown on a grid and participants are asked to point to locations in the order they had appeared

STM for Actions - body movement mirroring following an example by instructor

STM for Odors - single or multiple smells offered, participants must choose if smell is same or new

STM for Hearing Impaired - similarity in signs can cause memory error

Working Memory - the proposed advancement and elaboration of STM

Working-memory model consists of four components (multicomponent model)

  • Phonological Loop

  • Visuospatial Sketchpad

  • Central Executive

  • Episodic Memory

Phonological Loop - similar to verbal short-term memory

  • Represents our brief storage of verbal material we use in rehearsal, verbal problem solving, and arithmetic

  • Brief, limited capacity, easily disrupted

Testing could be conducted with a digit or word span; working memory adds in a second processing task to be conducted simultaneously

  • To-be-remembered words are intermixed with true-false arithmetic problems

Visuospatial Sketchpad

Retains visual images

  • Pictures, imaged versions of words, mental representations

Spatial information

  • Locations of squares or pieces on a game board

A test would ask to remember a sequence on a checkerboard; working memory would ask to assess symmetry or patterns

Can be referred to as: visual-spatial; visual-spatial intelligence, visual-spatial memory; these terms are all used interchangeably

Central Executive - in control of attention

  • Focuses attention, allocates attention, or distributes attention across multiple tasks

  • Difficulty experiences when attempting two things at once can be due to our inability to focus full attention on each

    • Attention is a limited resource

  • Central executive acts as a “manager” between the STM and LTM

Episodic Buffer

Integrates information across:

  • Phonological and visual stores

  • Central executive

  • Encoding and retrieval from LTM

STM interacts with LTM to accomplish processing tasks

  • Episodic buffer acts like a bridge between the two, retrieving memories from the LTM to help assist in accomplishing more complex thinking tasks

Measuring Working Memory

Typically measured by the capacity to do two things at once, referred to as dual tasks

  • Example: 2+3=?; 4 × 2 = ?; 9 - 3 = ? While remembering all the answers

Or phonological & visuospatial stores, remembering a string of words while judging if object pairs are the same or different

  • N-back task - remembering a location or letter “n-steps back”

  • Participants must push a button to indicated whether the n position is the same letter, in the same position, etc.

Executive Functions - higher-level cognitive skills used to control and coordinate other cognitive abilities and behaviors

  • Directs mental processes such as short-term remembering, problem solving, language production and comprehension, decision-making

    • Example: preparing a meal for one’s family - all the steps for completion

    • Food prep, cook time, quantities, portions, etc.

Updating: updating the contents of working memory by adding or dropping information

Inhibition: overriding a dominant, automatic, habitual response

  • Stroop test: Red, Black, Blue, etc.

Shifting: ease of switching rules or strategies

  • Sorting blocks by color to sorting by shape

Flexibility: readiness to response to changed goals or priorities

Attention control: the ability to focus attention, avoid distraction, and switch attention readily

Consciousness & Working Memory

Is there a difference between the two? What is mind and what is consciousness?

The CE is the control of attention, suggesting something (or someone) directs and chooses what to attend to

  • Rehearsing words in the phonological store is essentially “talking to oneself”

Visual & verbal information originate in different sensory modalities and coded differently in the brain, yet the mind translates one to the other and combines them

Individual Differences

Aging and WM - slower response time and difficulty inhibiting distracting thoughts

Dementia and WM - AD can range from mild to profound, dual tasks come with impairment as compared to single task problems

Anxiety and WM - attention is diverted to preoccupation, self-criticism, and other forms of negative thinking

  • Negative self-talk engages the phonological store, negative self-image engages the visuospatial, etc.

Can contribute to stereotype threats - stereotype reinforcers for beliefs can inhibit memories

Multitasking - Several separate tasks being attempted simultaneously

At any one moment, only one task or step can be performed due to physical or cognitive limitations

  • Steps involved are interleaved (one task is stopped to start a second task)

  • Interruptions and unexpected outcomes lead to delays

  • Remembering to return to a task that has not yet been completed

Basically, multitasking occurs whether we like it or not

  • High stress positions require multiple actions to be taken throughout a process (medical, legal, business, etc.)

Supertaskers - two cooccurring processes with high stakes outcomes

  • Driving while texting or talking on the phone