Memory: Stages, Sensory/Short-Term/Working Memory, and Long-Term Memory – Detailed Notes

Overview of Memory: Stages, Processes, and Core Concepts

• Memory is conceptualized by types, stages, and processes. Major focus in this content:

  • Three memory stages: sensory memory, short-term (working) memory, and long-term memory (Atkinson & Shiffrin, 1968).

  • In a later section, the nature of long-term memory is discussed with emphasis on encoding, storage, and retrieval.

• Information flow across memory stages:

  • Information begins in sensory memory, moves to short-term/working memory, and may move to long-term memory.

  • Not all information passes through all stages; much is forgotten.

  • Whether information moves to longer-term storage depends on how it is attended to and processed.

Sensory Memory

• Sensory memory: brief storage of sensory information; acts as a buffer lasting very briefly unless attended to and passed on for further processing.

• Function: gives the brain time to process incoming sensations, creating the perception of an unbroken stream rather than a series of discrete events.

• Subtypes:

  • Iconic memory (visual): first studied by George Sperling (1960).

  • Display duration: about $50\,\text{ms} = \frac{1}{20} \text{s}$.

  • Experiment: participants saw a grid of letters for a very brief time and were asked to report letters from a row cued after display offset.

  • Finding: participants could report almost all letters from the cued row when cued quickly after display removal, indicating access to all letters in iconic memory but that recall is limited by the brief duration.

  • Conclusion: iconic memory lasts only a fraction of a second.

  • Eidetic imagery (photographic memory): some individuals report the ability to recall details of an image for longer periods, sometimes linked to autism; reports of lasting visual detail can occur in some individuals.

  • Echoic memory (auditory): lasts longer than iconic memory, up to about $4\,\text{s}$ (Cowan, Lichty, & Grove, 1990).

• Examples and notes:

  • Eidetic memory in hearing has some evidence but is less common than visual eidetic memory.

  • Mozart anecdote: some claim eidetic memory for music; historical accounts (Solomon, 1995).

Short-Term Memory (STM) and Working Memory

• Entry to STM: most sensory information is forgotten unless attended to for memory goals; attended information may pass into STM.

• STM characteristics:

  • Small amounts of information held temporarily; duration typically more than a few seconds but usually less than one minute (Baddeley, Vallar, & Shallice, 1990).

  • Not just a passive store; involves processing operations known as working memory.

• Working memory: a set of memory procedures/operations that manipulate and work with information in STM; not merely a storage system.

• Example task illustrating working memory and central executive: a sequence where you solve math problems while maintaining following letters (e.g., answer questions like $Is\ 10 \times 2 - 5 = 15?$ and remember the following letter).

• The central executive:

  • Directs attention and processing to optimize performance.

  • Directs the rehearsal process and simultaneous mental imagery (e.g., forming an image of the list of letters).

  • Uses strategies best suited for the task and integrates information from other memory systems.

• Capacity and decay in STM:

  • STM is limited in both duration and capacity.

  • Peterson & Peterson (1959): when participants memorized a list of three-letter strings and performed a distracting task (counting backward by threes), the material decayed rapidly; by about $18\,\text{s}$ it was virtually forgotten.

  • Without rehearsal, information decays quickly from STM (maintenance rehearsal helps prevent decay).

Maintenance Rehearsal and STM Capacity

• Maintenance rehearsal: repeating information mentally or aloud to keep it in memory long enough to use or transfer to long-term memory.

• If rehearsal continues, information can stay in STM until rehearsal stops.

• STM capacity limits: relatively small; typical digit span ranges.

• Example activity: a digit string task where you read rows of numbers at about one digit per second, then write down as many digits as you can after each row. This illustrates how performance declines with longer rows.

Digit Span, Chunking, and the Miller Idea

• Digit span findings:

  • On average, adults can hold between $5\text{ and }9$ digits in STM, with an average around $7$.

  • The empirical rule often cited is Miller’s classic "magic number": $7 \pm 2$ items can be held in short-term memory.

• Limitation: even with the upper bound around $9$, large information sets require strategies to expand capacity.

• Chunking as a memory expansion strategy:

  • Chunking groups information into smaller, meaningful units (chunks), increasing the effective number of items stored.

  • Example: remember the string $XOFCBANNCVTM$ (12 letters) is difficult, but chunking into four sets of three letters each (e.g., corresponding to four TV stations) makes it easier.

  • Result: number of items to remember drops from 12 to 4 chunks.

Expertise, Chunking, and Memory Organization

• Experts vs. novices demonstrate the power of chunking in memory tasks:

  • Chess study (Simon & Chase, 1973): chess masters recalled positions from real-game layouts much better than novices, due to chunking into larger meaningful layouts and seeing the big picture.

  • When presented with random positions (unrelated to real games), both groups performed poorly; the chunking advantage disappeared when the layouts could not be organized into meaningful chunks.

  • Basketball recall shows a similar pattern: experts recall actual basketball positions better than nonplayers when the positions reflect game context; real-world meaningful chunks aid memory (Didierjean & Marmèche, 2005).

• Implications: chunking relies on prior knowledge and schema; memory is improved when information can be organized into meaningful patterns.

Long-Term Memory (LTM)

• Pathways beyond STM: information that passes STM may enter LTM, where it can be stored for days, months, or years.

• LTM capacity and permanence:

  • Large capacity; no known fixed limit to what can be remembered, though forgetting occurs for some information over time (Wang, Liu, & Wang, 2003).

  • Some information is forgotten after encoding; other information can remain with long-term storage indefinitely.

• Long-term memory processes (to be covered in the next section): encoding (how information gets into memory), storage (maintenance over time), retrieval (accessing stored information).

Key Takeaways

• Memory is the ability to store and retrieve information over time.

• Active cognitive processing ensures memory is not a perfect replica of experience.

• Information processing begins in sensory memory, moves to short-term memory, and eventually to long-term memory.

• Maintenance rehearsal and chunking help keep information in short-term memory.

• Long-term memory has a large capacity and no known limit in principle.

Exercises and Critical Thinking

• 1. List situations in which sensory memory is useful for you. Consider what experience would be like without sensory memory.

• 2. Describe a situation in which you need to use working memory to perform a task or solve a problem. How do your working memory skills assist you?

Connections to Foundational Principles and Real-World Relevance

• The multi-stage model aligns with foundational cognitive psychology principles of information processing: input, encoding, storage, retrieval.

• Chunking demonstrates how prior knowledge and pattern recognition expand capacity, a concept used in education, cognitive training, and expertise development.

• The distinction between maintenance rehearsal and deeper encoding (elaborative rehearsal, imagery, organization) underpins effective study strategies and learning outcomes.

• The role of the central executive emphasizes that attention and control processes shape memory performance, with implications for multitasking and cognitive load management.

Formulas and Numerical References (LaTeX)

• Iconic memory duration: $50\,\text{ms} = \frac{1}{20}\,\text{s}$

• Echoic memory duration: $4\,\text{s}$

• Short-term memory capacity (typical): $5 \leq \text{digits} \leq 9, \quad \text{average} \approx 7$

• Miller’s magic number: $7 \pm 2$

• Fractional duration concept: $\frac{1}{20}\text{ s}$

• Chunking reduces memory load from 12 items to 4 chunks in the example: (12 items) → (4 chunks)

• Real-world context references: Atkinson & Shiffrin (1968); Baddeley, Vallar, & Shallice (1990); Sperling (1960); Cowan, Lichty, & Grove (1990); Unsworth & Engle (2007); Solomon (1995); Wang, Liu, & Wang (2003); Didierjean & Marmèche (2005).