Memory Functions and Structures

Introduction to Memory

  • Photographs can trigger memories and bring past experiences back to life (credit: modification of work by Cory Zanker).

  • Consider a day without the ability to remember anything learned.

  • Loss of memory complicates basic tasks, such as dressing, eating, or recognizing people in one’s house.

  • Memory is essential for processing and storing information.

8.1 How Memory Functions

Learning Objectives

  • By the end of this section, you will:

    • Discuss the three basic functions of memory.

    • Describe the three stages of memory storage.

    • Distinguish between procedural and declarative memory, and between semantic and episodic memory.

Memory as an Information Processing System

  • Memory functions similarly to a computer with three main processes:

    • Encoding: Input of information into the memory system.

    • Storage: Retention of the encoded information.

    • Retrieval: Getting the information back into awareness.

Encoding

  • Definition: The initial step to get information into memory through sensory input where information is labeled, coded, organized, and connected.

  • Types of encoding:

    • Automatic Processing: Involuntary encoding of details like time, space, frequency, and meanings without conscious effort.

    • Effortful Processing: Requires attention and conscious effort to encode information (e.g., studying for a test).

Effective Encoding Example

  • When given confusing statements to recall:

    1. The notes were sour because the seams split.

    2. The voyage wasn't delayed because the bottle shattered.

    3. The haystack was important because the cloth ripped.

    • Prompting with context (bagpipe, ship christening, parachutist) improves recall.

Types of Encoding

  • Semantic Encoding: Focuses on the meaning of words, demonstrated by categorizing words based on their meaning (Bousbeld, 1935).

  • Visual Encoding: Involves encoding images, tends to make recall easier for concrete imagery (e.g., dog, book) compared to abstract terms (e.g., truth, value).

  • Acoustic Encoding: Involves the encoding of sounds, often utilized in educational contexts (e.g., songs for learning).

Semantic Processing Study (Craik & Tulving, 1975)

  • Words encoded semantically were recalled better than those encoded visually or acoustically.

  • Self-Reference Effect: Better retention of information related to oneself (Rogers, Kuiper, & Kirker, 1977).

Storage

  • Storage: Creation of a permanent record of information. Information must pass through three stages:

    • Sensory Memory: Very brief storage of sensory information (up to a couple of seconds).

    • Short-Term Memory (STM): Temporary storage lasting 15 to 30 seconds. Takes incoming sensory information.

    • Long-Term Memory (LTM): Continuous storage of information with virtually unlimited capacity.

Atkinson-Shiffrin Model (1968)

  • Memory storage involves stages: Sensory memory → Short-term memory → Long-term memory.

Baddeley and Hitch's Working Memory Model (1974)

  • Suggests short-term memory has different forms:

    • Visuospatial Sketchpad: Visual and spatial information.

    • Episodic Buffer: Integrates and processes information.

    • Phonological Loop: Deals with verbal and auditory information.

Sensory Memory

  • Briefly holds sensory stimuli before the information fades or is discarded. Information deemed valuable may enter short-term memory.

Short-Term Memory (STM)

  • Processes information and links it with long-term memory. Capacity of STM is typically around 7 ± 2 items as reported by George Miller (1956).

  • Active Rehearsal: Repeating information to move it from STM to LTM.

  • Elaborative Rehearsal: Connecting new information with existing knowledge (e.g., remembering a phone number by linking it to a known area code).

Capacity and Duration of Short-Term Memory

  • Magic Number: 7 ± 2; more contemporary findings suggest 4 ± 1 (Cowan, 2010).

  • Memory Trace Decay: Information retention diminishes over time (Peterson and Peterson, 1959); proactive interference occurs when prior information interferes with new learning.

Long-Term Memory (LTM)

  • Unlimited storage of information, organized in semantic networks. Spreading activation occurs when part of a network is activated, easier access to related concepts.

  • Two categories:

    • Explicit (Declarative) Memory: Conscious recall of facts/events (e.g., studying for exams).

    • Episodic Memory: Personal experiences (e.g., last birthday).

    • Semantic Memory: Facts and concepts (e.g., definition of psychology).

    • Implicit Memory: Non-conscious memories affecting behaviors (e.g., skills like riding a bike).

    • Types include:

      • Procedural Memory: Skills and actions (e.g., driving).

      • Priming: Exposure to a stimulus affects response to another stimulus.

      • Emotional Conditioning: Classics link conditioning to emotional responses.

Hyperthymesia

  • An extraordinary ability to recall past events vividly, exemplified by Marilu Henner, who possesses hyperthymesia, remembering extensive detail about her life.

Retrieval

  • Definition: Moving information from long-term memory to awareness (similar to finding a saved file on a computer).

Types of Retrieval Techniques

  • Recall: Accessing information without cues (e.g., essay tests).

  • Recognition: Identifying learned information with cues (e.g., multiple-choice tests).

  • Relearning: Learning previously learned information again (e.g., language learned in high school).

8.2 Parts of the Brain Involved with Memory

Learning Objectives

  • Explain brain functions involved in memory.

  • Recognize the roles of the hippocampus, amygdala, and cerebellum.

Scientific Research on Memory Storage

  • Karl Lashley’s research exploring the engram, which is not confined to a single part of the brain but distributed across various regions.

  • Equipotentiality Hypothesis: Suggests if memory area is damaged, other areas can compensate.

  • Eric Kandel’s work has highlighted memory mechanisms at the synaptic level involving neural circuits and neurotransmitters.

Brain Structures Involved

  • Hippocampus: Key in forming new memories, especially declarative memories; crucial for memory consolidation. Damage results in inability to form new semantic knowledge, demonstrated in the case of patient H.M.

  • Amygdala: Involved in emotion regulation and impacts memory storage; regulates how emotional events are processed as memories.

  • Cerebellum: Processes procedural memories (skills and actions).

  • Prefrontal Cortex: Involved with various memory tasks, emphasized during semantic processing.

Neurotransmitters and Memory

  • Neurotransmitters critical for memory include:

    • Epinephrine

    • Dopamine

    • Serotonin

    • Glutamate

    • Acetylcholine

  • Strong emotional events release neurotransmitters that enhance memory formation, a phenomenon supported by the arousal theory.

Flashbulb Memories

  • Exceptionally detailed recollections of significant emotionally-charged events (e.g., learning about 9/11).

8.3 Problems with Memory

Learning Objectives

  • Compare and contrast types of amnesia.

  • Discuss unreliability of eyewitness testimony.

  • Discuss encoding failure and various memory errors.

  • Compare and contrast types of interference.

Amnesia

  • Definition: Long-term memory loss due to factors such as disease or trauma.

    • Anterograde Amnesia: Inability to form new memories after trauma. Linked to hippocampal damage (e.g., patient H.M.).

    • Retrograde Amnesia: Loss of memory for events before the trauma.

Memory Construction and Reconstruction

  • Memory Construction: Process of forming new memories.

  • Memory Reconstruction: The retrieval process where old memories are modified and can be prone to inaccuracies.

Suggestibility and Errors

  • Suggestibility: Misleading information from external sources affecting memory recall.

  • Numerous cases, including false eyewitness identifications, demonstrate the fragility of memory.

Eyewitness Misidentification

  • Misleading identifications can lead to wrongful convictions; prominent case of Ronald Cotton showcases this issue.

Misinformation Effect

  • Following exposure to misleading information, an individual's recall of the original event can be distorted, demonstrated in Loftus's studies.

Forgetting Causes

  • Encoding Failure: Memory loss can occur when the memory is never stored in the first place (e.g., details of a penny).

  • Memory Errors:

  • Schacter’s seven sins categorize memory failures into forgetting, distortion, and intrusion.

  • Types include: Transience, absentmindedness, blocking, misattribution, suggestibility, and bias.

  • Forgetting type:

    1. Transience - accessibility of memory decreases over time (storage decay)    

    2. Absentmindedness - forgetting caused by lapses in attention

    3. Blocking - accessibility of information is temporarily blocked (tip-of-the-tongue phenomenon)

  • Distortion Type:

    1. Misattribution - Source of memory is confused

     2. Suggestibility - False memories

     3. Bias - Memories distorted by current belief system

  • Intrusion:

    • Persistence -  inability to forget undesirable memories 

Interference in Memory

  • Proactive Interference: Old information hinders recall of new information (e.g., switching phone numbers).

  • Retroactive Interference: New information interferes with the recall of older information.

8.4 Ways to Enhance Memory

Learning Objectives

  • Apply memory-enhancing strategies and effective study techniques.

Memory-Enhancing Strategies

  • Techniques such as rehearsal (conscious repetition), chunking (organizing information), and elaborative rehearsal (linking new information with existing knowledge) can enhance memory.

  • Mnemonic devices serve as powerful memory aids for organizing large amounts of information effectively.

    • example: PEMDAS(Parentheses, Exponents, Multiplication and Division, Addition and Subtraction) is a mnemonic device frequently used in math to remember the order of operations.

Study Techniques

  • Self-Referencing: Connects material to personal experiences for better recall.

  • Distributed Practice: Encourages spreading study over time instead of cramming.

  • Active Review & Chunking: Organizes and practices information efficiently to avoid feeling overwhelmed.

  • Stay Focused and Healthy: Managing distractions, engaging in physical exercise, and ensuring ample sleep contributes positively to memory retention.