Week 4 - Mini-lecture 1: Sensory memory and short-term memory

The idea of compartmentalizing memory isn't new; it can be traced back to William James in the late 19th century.
James distinguished between primary and secondary memory, a distinction not commonly used today.

Primary Memory:
- Refers to things we're currently aware of i.e. the contents of consciousness.
- For example, being aware of the desk, computer screen, and plants while recording a lecture video or feeling clothes on your body.
Secondary Memory:
- Mental representations of things not currently in our consciousness.
- For example, recalling a third-grade teacher's name requires retrieval from secondary memory into primary memory.
- Corresponds to retrieving long-term memory into short-term memory in modern terms.
Retrieval Process:
- The act of bringing information back into awareness; a key concept to be revisited.

Primary Memory (James):
- Sensory Memory
- Short-Term Memory
- Working Memory: Involves accessibility to our consciousness
Secondary Memory (James):
- Long-Term Memory
Long-Term Memory Distinctions:
- Declarative (Explicit) Memory
  - Effortful recall e.g., recalling the year of the moon landing.
- Non-Declarative (Implicit) Memory
  - Automatic recall e.g., memory of buttering toast.
Motor Skills:
- Typically implicit memories e.g., riding a bike.
- Difficult to describe or declare the actions involved, yet the memory is retained.
Video Focus:
- Sensory Memory
- Short-Term Memory
- Working Memory (in Mini Lecture Video Two)

Also known as the multi-store model of memory.
Information Processing: Information is passed between different memory stores.
Sensory Memory:
- Input from the external world (sight, hearing, taste, smell).
- Brief duration.
Short-Term Memory:
- Attention to sensory memory transfers information.
- Brief duration.
- Rehearsal: Helps retain information and increases the chance of encoding into long-term memory.
Long-Term Memory:
- Permanent store of memories spread throughout the brain.
- Includes past experiences, knowledge, and facts.
- Retrieval: Memories are retrieved back into short-term memory/conscious awareness.
Overall Idea:
- Different stores of memory exist.
- Processing involves passing information between these stores.

Sensory Memory: Seeing the pizza store's number on the computer screen, the individual finds the number 555-5100.
Short-Term Memory:
- The number is transferred here but remains for a limited time.
- Rehearsal: Repeating 555-5100 to keep it in short-term memory.
Long-Term Memory:
- Encoding: Using strategies to memorize the number for future use by repeating it and linking it to other things in life.
- Retrieval: Recalling the number from long-term memory into short-term memory when needed after exam revision.
- Illustrates all stores of memory in action.

Buffer: A buffer of incoming sensory information, holding a lot of information briefly.
Capacity: Thought to be extremely large.
Duration: Extremely short.
Different Stores: Different stores for each sense.
- Vision: Iconic memory.
- Hearing: Echoic memory.

Sensory memory for visual information.
Persistence of Vision: New sensory information blends with existing information in iconic memory.
- Example: Moving a sparkler at night creates a perceptual trail.
Stroboscope: An optical illusion toy that demonstrates persistence of vision.
Film Strips: Illusion of motion explained by iconic memory.
- Films show 24 still images per second.
- New information overwrites old information fast enough to perceive continuous movement.

A ball with red, blue, and green lights appears purple when still.
When twirled, the individual red, blue, and green lights become visible.
Explanation: Brain merges the rapidly changing colors into one when the ball is still.

Sensory memory for auditory information.
Importance: Speech perception and conversation depend on it.
Function: Allows us to remember what was said at the start of a sentence to understand the whole sentence.
Example: Asking a distracted person, \"What time is it?\" and before the question is repeated, they recall and answer it.

Sperling's Experiment (1960):
- Purpose: Measure the duration of iconic memory.
- Method: Displaying letters briefly and asking participants to recall them.
Whole Report:
- Participants recall as many letters as possible. Around 4-5 i.e. $(\frac{1}{3})$ of the 12 letters correctly.
Partial Report:
- Participants hear a tone indicating which row of letters to report, performance jumps from 37% to about 83%.
Results:
- Suggests sensory memory is large in capacity.
- Participants are cued to report a specific row of letters after a delay.
- The delayed tone results:
  - Performance rapidly worsens as the delay increases e.g., reporting 'K' and others, but by the last, the memory is lost.
  - The duration of iconic memory is found to be less than one second.
Echoic Memory:
- Similar experiments determine echoic memory duration, which decays less rapidly than iconic memory.

Material in short-term memory can be rehearsed through active processes.
Example:
- Repeating a multi-factor authentication code (e.g., 233450) to remember it.
- Rehearsal prolongs the duration, can be done for long periods to retain.
Characteristics:
- Conscious and effortful.
- If focus is lost, information decays.

Digit Span Task:
- Classic measure used in neuropsychological studies.
- Process: Repeating numbers back, increasing in difficulty of each series/level.
- Typical result (Miller's Law): People recall between 5 and 9 items (7 ± 2).
- In these series, the number of difficulty increase with each set of numbers: 43, 749, 8521, 27350….
Chunking:
- Strategy to increase short-term memory capacity.
- Example: Recognizing that 1946 (series 6) is a date and grouping the numbers.

Taking smaller items and joining them together increases the capacity of short-term memory.
Example with Lists of Letters:
- List 1: Hard to chunk (random letters).
- List 2: Can be chunked into internet slang/abbreviations like IDK, LMK, OMG etc. This reduces the number of items to remember.