memory

Definition: Coding refers to the way information is processed and stored in different memory stores.

Short-Term Memory (STM) → Acoustically Encoded
This means information is stored in STM based on how it sounds. If words sound similar, they can be easily confused.
Long-Term Memory (LTM) → Semantically Encoded
This means information is stored in LTM based on its meaning. If words have similar meanings, they can be easily confused.
Key Study: Baddeley (1966)
- Participants were given four lists of words:
  - Acoustically similar (e.g., cat, cab, can)
  - Acoustically different (e.g., dog, pit, cow)
  - Semantically similar (e.g., large, big, huge)
  - Semantically different (e.g., good, hot, safe)
- When asked to recall the words immediately (STM), they made more mistakes with acoustically similar words.
- When asked to recall the words after 20 minutes (LTM), they made more mistakes with semantically similar words.
- This shows STM relies on sound, and LTM relies on meaning.

Definition: Capacity is the amount of information that can be held in a memory store.

STM Capacity: 7 ± 2 items (Between 5 and 9 items)
- Proposed by Miller (1956) – He noticed patterns in everyday life (e.g., 7 days of the week, 7 musical notes).
- Chunking (grouping information) helps increase STM capacity. For example, remembering "BBC ITV USA" instead of "B B C I T V U S A."
LTM Capacity: Unlimited
- There is no known limit to how much we can store in LTM.
Key Study: Jacobs (1887)
- Participants had to recall strings of letters or numbers in the correct order.
- Findings:
  - Letter span = 7.3
  - Digit span = 9.3 (Easier to recall numbers than letters)

Definition: Duration is how long information can be stored before it is lost.

STM Duration: 18–30 seconds
- Key Study: Peterson & Peterson (1959)
  - Participants were given random consonant syllables (e.g., “TRG”) and a 3-digit number.
  - They had to count backwards from the number (to prevent rehearsal).
  - Findings:
    - After 3 seconds → 80% recall
    - After 18 seconds → Less than 10% recall
  - This shows STM lasts about 18-30 seconds unless rehearsed.
LTM Duration: Unlimited
- Key Study: Bahrick et al. (1975)
  - Studied 396 people who graduated up to 46 years earlier.
  - Participants had to recall classmates' names from yearbook photos.
  - Findings:
    - 15 years later → 90% accuracy
    - 46 years later → 70% accuracy
  - This shows LTM can last a lifetime, especially for meaningful information.

✅ Strength – Bahrick et al. (1975) is Realistic

Uses real-life memories, so findings are ecologically valid (realistic and generalisable to everyday life).

❌ Weakness – Peterson & Peterson (1959) Uses Artificial Stimuli

Using nonsense syllables does not reflect real memory use, meaning it lacks mundane realism (real-world relevance).

❌ Weakness – Miller’s Estimate May Be Too High

Newer research suggests STM capacity is closer to 4 chunks, not 7.
This suggests Miller overestimated because he did not control confounding variables.

Definition: The Multi-Store Model of Memory (MSM) explains how information moves through three types of memory storage:

Function: Takes in information from the environment through the senses.

Different Types of Sensory Memory:
- Echoic memory → For sounds
- Iconic memory → For visual images
Characteristics:
- Capacity → Very large (receives lots of sensory info)
- Duration → Less than half a second
- Coding → Depends on the sense (e.g., auditory for sounds, visual for images)
Information only moves to STM if we pay attention to it.

Characteristics:
- Coding → Acoustic (sound-based)
- Capacity → 7 ± 2 items (Miller)
- Duration → 18-30 seconds (Peterson & Peterson)
Maintenance rehearsal: Repeating information to keep it in STM.
If rehearsed enough, information moves into LTM.

Characteristics:
- Coding → Semantic (based on meaning)
- Capacity → Unlimited
- Duration → Lifetime (Bahrick et al.)
Retrieval: Bringing information from LTM back into STM when needed.
If we don’t rehearse or use information, we forget it.

✅ Strength – Supports Differences Between STM and LTM

❌ Weakness – LTM is Not a Single Store

Tulving (1985) showed LTM is made of:
- Episodic memory → Personal experiences
- Semantic memory → Facts and knowledge
- Procedural memory → How to do things (e.g., riding a bike)
The MSM treats LTM as one store, which is incorrect.

❌ Weakness – Overemphasis on Rehearsal

The MSM states more rehearsal = better memory.
Craik & Watkins (1973) suggest elaborative rehearsal (making meaningful links) is better than just repeating.

❌ Weakness – STM is Not a Single Store