Memory Systems: Sensory, Short-Term, Working, and Long-Term

Memory Stages: Sensory, Short-Term, and Long-Term

Sensory Memory

• Definition and Purpose: It holds information about a perceived stimulus for just several seconds after the stimulus disappears. This allows a mental representation of the stimulus to remain briefly for further processing or to fade if deemed unimportant. Atkinson and Shifrin suggested sensory memory exists for all five senses, but research has focused primarily on two:

Iconic Store (Visual Sensory Memory)

• Stimuli: Stores visual stimuli or 'icons'.
• Accuracy: Remarkably accurate and contains much more information than people can report before it fades.
• Duration: Approximately $0.5 ext{ seconds}$.
• Capacity: Can hold about $9 ext{ or } 10 ext{ items}$ in that brief duration.
• Example: Seeing a picture from the Netherlands and then trying to recall what was in it immediately after it's removed.

Echoic Store (Auditory Sensory Memory)

• Stimuli: Stores auditory stimuli or 'echoes'.

• Capacity: Can hold about $5 ext{ items}$, which is fewer than the iconic store.

• Duration: Holds items longer than iconic memory, for about $3 ext{ to } 4 ext{ seconds}$.

• Types: Some researchers suggest humans may have two types:

  • One for speech, located in the left hemisphere.
  • One for non-speech, located in the right hemisphere.

• Transition to Short-Term Memory: Many stimuli pass through the sensory register and fade. Others make a greater impression, and information is passed on to short-term (or working) memory.

Short-Term Memory vs. Working Memory

• Working Memory: This is the active memory resource used to accomplish tasks. It involves reasoning, language comprehension, solving problems, and achieving goals. It is your active memory, where information is manipulated and processed.
• Short-Term Memory (STM): This is likely a component of working memory. It holds a small amount of information in your conscious mind for about $20 ext{ seconds}$. Information in STM fades unless a deliberate attempt is made to maintain it longer.
• Distinction: While often used interchangeably, they are distinct. Working memory is an active process of manipulation, whereas short-term memory is primarily a temporary storage unit.

Short-Term Memory Storage

• Limited Capacity: STM is quite limited, demonstrated by the difficulty in remembering a new acquaintance's name a minute or two after meeting them.
• Analogy: Like a lunch counter with a limited number of seats (e.g., $7 ext{ seats}$). New information 'bumps' current information out of consciousness.
• Duration: Information can be held for about $20 ext{ seconds}$.

Improving Storage in Short-Term Memory

• Rehearsal:
  • Maintenance Rehearsal: Used to maintain what is currently in STM by repeating it over and over. This is a shallow level of processing.
  • Example: Repeating a grocery list (milk, bread, eggs) to remember it until items are acquired.
  • Recall Test Example: Recalling letters like RQLBF or TMCXPAHJ relies on maintenance rehearsal.
• Chunking: Allows remembering more information by grouping individual items into meaningful units.
  • Example: The list CIAFBIACTIRSUSANBC is easier to remember than CBNASRITCAIBFAIY (the same letters in reverse order without meaningful chunks) because it groups letters into acronyms like CIA, FBI, ACT, IRS, USA, NBC. Each acronym becomes one 'unit' instead of multiple letters.

Capacity of Short-Term Memory

• George Miller (1956): Suggested the capacity is about $7 ext{ items} ext{ } ext{plus} ext{ } ext{or} ext{ } ext{minus} ext{ } 2$ ($5 ext{ to } 9 ext{ items}$).
• More Recent Research: Indicates a potentially smaller capacity, around $4 ext{ items} ext{ } ext{plus} ext{ } ext{or} ext{ } ext{minus} ext{ } 1$ ($3 ext{ to } 5 ext{ items}$).

Short-Term Memory Retrieval

• Retrieval from STM is generally efficient.
• Position Effect: The position of an item in a list affects how easily it's recalled.
  • Memory Test Example: List of items: table, cloud, book, tree, shirt, cat, light, bench, chalk.
  • Recency Effect: Refers to superior recall of words that occur at or near the end of the list (e.g., bench, chalk). This occurs because these items are still present in STM (they haven't been 'bumped out').
  • Primacy Effect: Refers to superior recall of words that occur at or near the beginning of the list (e.g., table, cloud). This happens because these words were rehearsed and transferred to long-term memory.
  • Items in the middle of the list (e.g., shirt, cat, light) are often forgotten.

Baddeley's Working Memory Model

This model further distinguishes working memory from the simpler process of short-term memory and includes three major components:

• Phonological Loop:
  • Function: Stores and rehearses speech-based information.
  • Capacity: Allows repetition of about $7 ext{ items}$ immediately after hearing them.
  • Importance: Essential for understanding long sentences by maintaining the start of the sentence in memory to connect with the end.
• Visuospatial Sketchpad:
  • Function: Stores and manipulates visual and spatial information (e.g., remembering a party scene from a picture).
  • Distinction with Phonological Loop: You can perform an auditory task (phonological loop) and a visual task (visuospatial sketchpad) simultaneously (e.g., looking at a picture while listening to someone describe it). However, you cannot do two auditory tasks (e.g., two conversations) or two visual tasks (e.g., watching two TVs) effectively at the same time; attention shifts between them.
• Central Executive:
  • Function: Governs shifts of attention and manages the activity of the phonological loop and visuospatial sketchpad. This ability to shift attention among a variety of tasks is considered the hallmark of good working memory.
  • Examples: Multitasking activities like doing laundry, watching a game, and grading papers, or an emergency room nurse responding to a