Study Notes on Short Term Memory

Short Term Memory: Berna Altunisik

Chapter Overview

  • Main Topics:

    • The Modal Model

    • Sensory Memory

    • Short Term Memory (STM)

    • Capacity of STM

    • Forgetting in STM

Understanding Memory

  • Definition: Memory refers to the processes involved in:

    • Retaining information

    • Retrieving information

    • Using information when original information is no longer present

  • Key Points:

    • Memory is not a single entity; there are various types and processes of memory.

    • Investigating these differences can reveal how memories are formed and retrieved.

The Modal Model of Memory

  • Developers: Atkinson and Shiffrin (1958)

  • Components:

    • Sensory Memory: Initial retention of sensory information.

    • Short Term Memory (STM): Temporary storage and manipulation of information.

    • Long Term Memory (LTM): Long-term storage of information.

  • Process: Input → Sensory Memory → Short Term Memory → Long Term Memory → (requires Rehearsal)

Sensory Memory

  • Definition: The initial, brief storage of sensory information.

  • Characteristics:

    • Retention is very brief (decays in less than a second).

    • Capable of holding a large amount of information.

  • Types of Sensory Memory:

    • Iconic Memory: Visual sensory memory.

    • Echoic Memory: Auditory sensory memory.

Sperling's Experiment (1960) - Sensory Memory Demonstration

  • Objective: To explore the capacity and duration of sensory memory.

  • Procedure:

    1. An array of letters is flashed quickly to participants.

    2. Participants report as many letters as they can.

  • Results:

    • Whole Report: Average of 4.5 out of 12 letters (37.5% accuracy).

    • Partial Report: Average of 3.3 out of 4 letters (82% accuracy).

    • Delayed Partial Report: Performance decreases rapidly when cues are delayed.

Conclusions from Sperling (1960)

  • Findings:

    • Partial report yields higher capacity due to quick retrieval of information.

    • Significant decay occurs in sensory memory, leading to forgotten items during reporting.

    • Validates the existence of iconic memory, suggesting brief retention of all visual stimuli before decay.

Short Term Memory (STM)

  • Definition: The memory system used for temporarily holding information.

  • Key Functions:

    • Acts as a present window for accessing both newly acquired information and information retrieved from LTM.

  • Characteristics:

    • Limited capacity; lasts 15-30 seconds.

    • Requires control processes such as rehearsal to maintain information.

Capacity of Short Term Memory

  • Digit Span Task:

    • Participants recall a set of digits after brief presentation.

    • Resulting recalled digits: 92158 and 40263908.

  • Findings:

    • Average STM capacity is approximately 5-9 units (George Miller's "The Magical Number Seven, Plus or Minus Two").

    • Discrepancies exist due to further research exploring limitations.

Change Detection Task

  • Objective: To identify which colored squares changed after brief display.

  • Results:

    • Indicated average short-term capacity of only 4 units, contrasting Miller's findings.

    • Noted increased opportunities for rehearsal in the Digit Span task may contribute to capacity differences.

Chunking in Short Term Memory

  • Definition: A mental process that combines several pieces of information into larger units (chunks).

    • Example: Grouping letters or numbers into recognizable patterns.

  • Implication: Allows individuals to overcome capacity limits of short term memory by transforming units into meaningful chunks.

Understanding Forgetting in Short Term Memory

  • Mechanisms of Forgetting:

    • Decay: As time passes, memory traces fade away.

    • Interference: New information interferes with the retrieval of current information.

  • Testing Decay vs. Interference:

    • Presenting sequences of numbers to analyze recall accuracy under conditions of delay vs. interference.

Evidence Supporting Interference Theory

  • Waugh & Norman (1965):

    • Results showed similar recall levels under slow vs. fast conditions, but accuracy decreased with an increasing number of intervening items.

  • Conclusion: Supports interference theory as the dominant explanation over decay for memory loss in STM.

Serial Position Curve

  • Concepts:

    • Primacy Effect: Easier recall for items at the beginning of a list (due to increased rehearsal).

    • Recency Effect: Easier recall for items at the end of a list (if recalled immediately).

  • Impact of Delay: Delaying recall affects recency effect but not primacy effect, as items at the beginning had more rehearsal opportunities.

Key Takeaways

  • Understanding the differences between sensory and short-term memory types.

  • Recognizing the functions and limitations of STM.

  • Noting rehearsal and chunking as methods to retain information in STM.

  • Comprehending the theories of decay and interference in relation to the serial position curve and memory retrieval.