Memory Processes and Capacity

Memory Processes

• Storage: Maintaining information for future use.
• Encoding: Transforming sensory input into a format for storage.
• Retrieval: Accessing and bringing stored information to awareness.

Capacity and Duration of Memory

Capacity of Short-Term Memory (STM)

• George Miller proposed a capacity of 5-9 items (often described as "the magic number 7, plus or minus 2").

Capacity of Long-Term Memory (LTM)

• Unlimited capacity for a lifetime.

Capacity of Sensory Memory

• Information from the environment is briefly and highly limited.

Duration of Short-Term Memory (STM)

• Temporary storage, limited capacity (5-9 items).
• Duration: About 20-30 seconds.

Duration of Sensory Memory

• Visual (iconic) memory: Less than a second.
• Auditory (echoic) memory: Up to a few seconds.

Duration of Long-Term Memory (LTM)

• Theoretically unlimited storage, maintained over time.

Multi-Store Model of Memory

• Information is lost/forgotten if selective attention isn't paid to it.
• Information in STM can decay (fade) or be displaced by new information if not rehearsed.

Memory Retrieval Types

• Recognition: Identifying previously learned information with cues (e.g., multiple-choice tests).
• Recall: Generating information from memory without cues (e.g., listing the planets).
• Relearning: Learning information faster when encountered again (showing memory traces remained).

Examples of Memory Retrieval

• Recalling facts (historical dates, formulas).
• Recognizing tasks (remembering to buy groceries).
• Recognizing a face/song.

Retrieval Cues

• Stimuli (like smells) that help access stored information.

Context-Dependent Memory

• Retrieval ability influenced by the context in which information was learned.
• Studying in the same environment as the exam is beneficial.

H.M.: A Case Study in Memory

• Suffered from severe seizures.
• Surgery aimed at alleviating seizures by removing parts of the hippocampus and surrounding temporal lobe structures.
• Surgery had a side effect of impairing the ability to form new long-term memories.
• Demonstrated the crucial role of the hippocampus for forming new long-term memories.

Major Structures of the Brain

• Cerebrum: Largest part, responsible for higher-level functions (thought, memory, language, consciousness).
  • Cerebral Cortex: Outer layer, divided into four lobes (Frontal, Parietal, Temporal, Occipital).
    • Functions vary by lobe (e.g., Frontal lobe involved in decision-making).
• Cerebellum: Coordinates movement, balance, posture.
• Brain Stem: Connects brain and spinal cord, controls basic life functions (breathing, heart rate).
  • Subdivisions (Medulla Oblongata, Pons, Midbrain))
• Hippocampus: Crucial for forming new memories.
• Amygdala: Plays a role in emotional memory.
• Cerebral Cortex: Involved in storing and retrieving long-term memories.
• Brain defects can impact memory.

Factors Influencing Individual Differences

• Genetics: Heredity, neurotransmitter levels.
• Environment: Upbringing, cultural influences, education, learning opportunities.
• Experiences: Personal experiences, trauma.
• Brain structure and function: Neurotransmitter imbalances, brain injuries.

The Human Brain: A Marvel of Complexity

• The human brain is a complex network of billions of neurons communicating through electrical and chemical signals.