Evaluation of Capacity Studies

The digit span studies have limitations:

1. Use of artificial stimuli (meaningless digits and letters)
2. Lack of validity in early research due to inadequate controls

However, consistent findings across multiple studies support the validity of the 7±2 capacity concept.

Research on Memory Duration

Memory duration refers to how long information is stored. STM typically holds information for 18-30 seconds, while LTM can store information indefinitely.

Peterson & Peterson Study (1959)

The Peterson and Peterson duration of STM experiment involved:

• 24 undergraduate students
• 8 tasks with consonant syllables and 3-digit numbers
• Backward counting to prevent rehearsal
• Recall attempts after 3, 6, 9, 12, 15, and 18 seconds

Findings suggested that STM has a short duration unless information is actively rehearsed.

Highlight: The Peterson & Peterson study demonstrated that without rehearsal, information in short-term memory decays rapidly, typically within 18-30 seconds.

Bahrick's Study on Long-Term Memory Duration (1975)

Bahrick's procedure:

• 392 American participants aged 17-74
• High school yearbook tests:
  1. Photo recognition test
  2. Free recall of classmates' names

Findings:

• 15 years post-graduation: 90% accurate in photo recall, 60% in free recall
• 48 years post-graduation: 70% accurate in photo recognition, 30% in free recall

Highlight: Bahrick's study suggests that the capacity of long-term memory is potentially unlimited, with some information persisting for decades.

Evaluation of Duration Studies

Limitations include:

1. Use of artificial stimuli in Peterson & Peterson's study
2. Potential lack of validity in early research due to inadequate controls

Example: The use of meaningless consonant syllables in Peterson & Peterson's study may not accurately reflect how people remember meaningful information in real-life situations.

These studies on coding, capacity, and duration provide valuable insights into human memory processes, despite their limitations. They form the foundation for our understanding of working memory models, semantic memory, and the distinctions between episodic and semantic memory.

The page details George Miller Psychology magic number 7 theory and related research on memory capacity.

Quote: "Miller observed everyday or significant practices and usually came in sets of 7"

Example: Seven days in a week and seven deadly sins demonstrate natural chunking of information

Highlight: The capacity of long-term memory appears unlimited, while STM capacity is more restricted

This section explores Peterson and Peterson duration of STM through detailed experimental procedures.

Definition: Duration refers to how long information remains stored in memory

Example: Participants had to remember consonant syllables while counting backward from three-digit numbers

The page also introduces Bahrick's study on long-term memory duration.

The final page critically evaluates the methodology of memory studies, particularly focusing on their ecological validity.

Highlight: The use of artificial stimuli in both Peterson and Peterson studies limits their real-world application

Vocabulary: Ecological validity refers to how well research findings can be applied to real-life situations

The Baddeley (1966 study) investigated how information is encoded in short-term memory (STM) and long-term memory (LTM). This research, along with studies on memory capacity and duration, provides crucial insights into human memory processes.

Baddeley's Experiment on Memory Coding

The Baddeley (1966 procedure) involved giving different word lists to four groups:

1. Acoustically similar words (e.g. cat, can, cab)
2. Acoustically dissimilar words (e.g. cat, few, pit)
3. Semantically similar words (e.g. great, large, big)
4. Semantically dissimilar words (e.g. small, big, medium)

Participants were asked to recall words immediately and after 20 minutes.

Baddeley (1966 findings) showed:

• Immediate recall was worse for acoustically similar words, suggesting STM uses acoustic encoding
• Delayed recall was worse for semantically similar words, indicating LTM uses semantic encoding

Highlight: The Baddeley experiment revealed that short-term memory relies on acoustic coding, while long-term memory utilizes semantic coding.

Vocabulary: Acoustic coding refers to remembering information based on how it sounds, while semantic coding involves storing information based on its meaning.

Evaluation of Baddeley's Study

A limitation of Baddeley's research was the use of artificial stimuli lacking personal meaning for participants. This may limit generalizability to real-world memory tasks, as people might use semantic coding even for STM when processing meaningful information.

Research on Memory Capacity

Memory capacity refers to how much information can be held at one time. While LTM is believed to have unlimited capacity, STM capacity has been extensively studied.

Digit Span Test (Jacobs, 1887)

Jacobs' procedure involved:

1. Presenting participants with increasing numbers of digits
2. Asking for immediate recall in the correct order
3. Continuing until participants failed to recall all digits correctly

Findings showed a mean digit span of 9.3 items and a letter span of 7.3 items, supporting the concept of "7+-2" as the capacity of short-term memory.

Definition: Digit span is the number of digits a person can recall in the correct order immediately after presentation.

Miller's Chunking Theory (1956)

George Miller observed that many everyday practices involve sets of 7 items (e.g., 7 days in a week, 7 deadly sins). This led to the theory that STM "chunks" information into groups of about 7 items.

Example: The "Magic number 7 psychology" concept suggests that people can typically remember 7 (plus or minus 2) chunks of information in their short-term memory.