cog 2.13

Overview of Short Term Memory

• Chapter five focuses on short term memory as part of a broader discussion about the memory system.

• Definition of Memory:

  • Memory involves storing and recalling thoughts, experiences, visuals, emotions, and information.

  • Memory consists of processes that include encoding (storing), retaining, and retrieving information.

Memory Models

• The discussion introduces models that researchers have proposed to understand memory processing.

• The Modal Model of Memory by Atkinson and Shiffrin describes three separate stores in the memory system:

  1. Sensory Memory:

     • Quickly holds vast amounts of sensory information for a brief moment (less than a second).

     • Filters through sensory input to decide what is worth processing.

     • Sensory memories include:

       • Iconic Memory: Visual sensory memory for images.

       • Echoic Memory: Auditory sensory memory for sounds, lasting slightly longer than visual memory.

  2. Short Term Memory (STM):

     • Actively processes selected information from sensory memory.

     • Holds less information for longer than sensory memory (approximately 15-30 seconds).

  3. Long Term Memory (LTM):

     • Holds information for extended periods, enabling recall of past experiences.

Sensory Memory Characteristics

• Sensory memory allows for immediate retention of a large amount of stimuli in a short period, providing flexibility to choose what to retain for further processing.

• Persistence of vision: phenomenon where visual information stays in our memory briefly, allowing us to perceive smooth motion (e.g., in film).

• Practical applications of persistence of vision include:

  • Films that use rapid frame sequences to create the illusion of motion.

  • LED signs and sparkler trails that visually merge sequential light patterns into fluid motion.

Key Research on Sensory Memory

• Roger Sperling's Study (Whole vs. Partial Report):

  • Showed participants a grid of letters for a fraction of a second, then asked them to recall them.

  • Whole Report Hypothesis: Participants struggled to recall all letters (average recall around 30%).

  • Partial Report Method: When vocal tones directed participants to specific rows after display, recall accuracy increased significantly (over 80%) if the tone was presented immediately after the visual stimuli.

  • Performance dropped with delays in tones, demonstrating the importance of timing in accessing memory.

Transition to Short Term Memory

• Short term memory processes and characteristics include:

  • Limited capacity in comparison to sensory memory.

  • Duration of holding information drastically shorter without rehearsal or active engagement.

  • Control processes (like rehearsal) are needed to maintain information in STM.

Strategies for Short Term Memory

• Maintenance Rehearsal: Repeating information to keep it active.

• Chunking: Grouping items into larger units of meaning as a way to enhance STM capacity.

The Brown-Peterson Task

• A classic task aimed at investigating short term memory:

  1. Participants see items (e.g., letters) followed by a distractor task (e.g., counting backwards).

  2. Studies demonstrated a rapid forgetting curve; performance in recalling the items significantly declined over time (e.g., recall accuracy dropped sharply after 15-30 seconds).

  3. Their findings led to distinctions between the effects of proactive interference (previous trials affecting recall of later trials) and retroactive interference (new information affecting recall of previous information).

Short Term Memory Capacity

• Defined through studies that measure how many items can fit in STM.

• Early researchers suggested the capacity of STM is

  • Seven Plus or Minus Two: Average human capacity for holding onto items in STM is around 5 to 9 items.

• Memory span tasks assess this capacity, showing individual differences in chunking abilities vary dramatically.

Chess Studies Example

• Distinguished chess players performed better than novices when recalling meaningful game sequences but struggled with random placements.

• Expert players utilized their knowledge to chunk information effectively, enhancing recall efficiency.

Final Insights

• Effective memory strategies include rehearsal and chunking to improve performance in recalling information.

• The importance of structure, meaning, and experience in facilitating memory encoding and recall is emphasized throughout the discussion.