Introduction to Memory Models and Stores

1. Overview of Memory Processing

Memory processing follows a continuous flow from environmental detection to long-term storage:

1. Sensation & Input

   • Environmental sensory inputs enter through sense organs.

   • Sensation detects far more information than the brain can actively pay attention to.

2. Sensory Memory Filtering

   • Sensory information is briefly held to allow time to evaluate its importance.

   • Unattended sensory data fades and is forgotten quickly.

3. Attention & Short-Term Memory

   • Paying attention selects specific information for further processing.

   • Information moves into awareness within short-term (working) memory.

4. Encoding & Long-Term Memory

   • Information is encoded into long-term memory by building connections with pre-existing knowledge.

   • Stored information can later be retrieved back into working memory when needed.

2. Sensory Memory Stores

Sensory memory maintains an exact copy of sensory information for a brief duration to allow selection of important signals.

2.1 Iconic Sensory Memory (Visual)

• Definition: Sensory store for visual inputs coming through the eyes.

• Capacity: Extremely large; holds virtually all visual input detected by photoreceptors.

• Duration: Less than $0.5\,\text{seconds}$.

• Sperling's (1960) Research:

  • Full Report Task: Participants presented with a grid of letters could only report $4$ or $5$ items before the visual image faded.

  • Partial Report Procedure: Sperling paired rows of letters with high, medium, or low auditory tones played immediately after visual stimuli vanished. Participants consistently reported any cued row with near $100\%$ accuracy.

  • Conclusion: Iconic memory holds a snapshot of the entire visual field, but it decays extremely rapidly to allow perception of real-time visual changes.

2.2 Echoic Sensory Memory (Auditory)

• Definition: Sensory store for auditory inputs coming through the ears.

• Capacity: Large; holds all ambient sounds detected.

• Duration: Approximately $2$ to $4\,\text{seconds}$.

• Function: Retains auditory signals long enough to synthesize meaningful streams (e.g., understanding the beginning of a spoken sentence by the time the speaker reaches the end, or counting bell tower rings after missing the initial chime).

2.3 Other Sensory Stores

• Tactile (Haptic), Olfactory (Smell), and Gustatory (Taste):

  • Hypothesized to work identically with large capacities and short durations suited to environmental change rates.

  • Difficult to study empirically in laboratory settings due to challenges in instantly presenting and clearing physical tactile, taste, or odor stimuli.

3. Short-Term Memory (STM) / Working Memory

3.1 Characteristics & Function

• Definition: The active workspace of memory containing information that an individual is consciously aware of and manipulating at any given moment.

• Duration: Approximately $15$ to $30\,\text{seconds}$ without active manipulation or rehearsal.

• Maintenance Rehearsal: Verbal or mental repetition of information resets the decay timer, sustaining items in working memory.

3.2 Capacity & Chunking

• Capacity Limits:

  • Classic view (Miller, 1955): $7 \pm 2$ items.

  • Modern research consensus: Approximately $4$ to $5$ active units or bits of information.

• Chunking:

  • The process of combining individual bits of data into single meaningful units (chunks).

  • Chess Master Demonstration:

  • Non-expert chess players can recall $4$ to $5$ individual chess piece locations from a board.

  • Chess masters can recall $4$ to $5$ entire standard game configurations because they chunk related piece configurations into single meaningful game states.

  • When presented with randomly placed pieces that cannot naturally occur in a game, chess masters perform identically to non-experts ($4$ to $5$ individual pieces), as standard chunking strategies fail.

4. Long-Term Memory (LTM)

4.1 Features of LTM

• Capacity: Unlimited; there is no physical limit to the volume of information stored.

• Duration: Potentially permanent / lifetime storage.

4.2 Encoding & Retrieval Mechanics

• Encoding: The mechanism of transferring information from short-term memory to long-term memory by building neural and conceptual connections to pre-existing knowledge.

• Retrieval: Transferring stored LTM content back into active working memory for conscious thought or application.

• Memory Network Architecture:

  • Memories consist of interconnected networks of concepts.

  • Strong Memory Traces: Formed by creating multiple, diverse connections to a concept rather than repeating the same thought path.

  • Studying Application: Viewing concepts through different contexts and varied real-world examples creates multiple retrieval pathways, making information easier to locate and access later.