Long-Term Memory: Explicit vs Implicit; Amnesia, Eyewitness Memory, and Interference

Source framing and exam strategy

• The instructor notes that there can be slight variations between textbook terms and class/lecturer terminology.
• The book provides base definitions; the exam will emphasize the learning objectives identified for the course.
• There is a full list of learning objectives on campus (Unit One) that students find helpful for study planning.
• The teacher will not test material not related to learning objectives; focus study on those objectives.
• Emphasis on comprehensive, test-ready understanding rather than random minutiae from the book.

Big picture: long-term memory (LTM)

• LTM splits into two broad subtypes: explicit memory and implicit memory.
• Goal: understand differences between the two types and their subcomponents, with real-world examples and clinical/forensic relevance.

Explicit memory (declarative memory)

• Definition (for this course): the process of recalling information intentionally.
• Divides into two major subtypes:
• Semantic memory: knowledge of facts, definitions, and general knowledge.
• Episodic memory: memory for personally experienced events or episodes.
• Examples from lecture:
• Recognizing a public figure (e.g., William Eilish) as an example of semantic/known facts stored in long-term explicit semantic memory.
• Knowing the definition of explicit memory itself resides in semantic memory.
• Key point about episodic memory:
• Memories of personal episodes, with both positive and negative emotional valence (e.g., first kiss, a notable Auburn game moment).

Implicit memory (non-declarative memory)

• Definition: memory for information we recall without conscious deliberate effort.
• Two main facets emphasized in lecture:
• Procedural memory: memory for motor skills and actions (how to do things).
• Priming: exposure to one stimulus influences response to a later stimulus, often without conscious awareness.
• Examples discussed:
• Procedural: tying shoes, driving a car, pumping gas, timekeeping actions when you’ve done them many times.
• Priming examples: the word-framing exercise (e.g., subliminal or contextual cues influencing word association).
• Additional implicit forms exist, but the lecture focuses on the two above.

Explicit vs. implicit memory: quick synthesis

• Explicit memory requires conscious recall; implicit memory operates automatically and without deliberate recollection.
• Within explicit memory, semantic memory encodes facts and general knowledge, while episodic memory encodes personal experiences.
• Within implicit memory, procedural memory underlies skills and habits, while priming affects perception and response speed based on prior exposure.
• Conceptual relationships can be summarized as:
• LTM = E  I,
  \ E = S ul
  Ep,
  I = P ul
  Prm,
• where E = explicit memory, I = implicit memory, S = semantic, Ep = episodic, P = procedural, Prm = priming.

Illustrative examples and terminology from the lecture

• Semantic memory example: knowing the definition of explicit memory is part of semantic memory.
• Episodic memory example: personal memories like a memorable game moment.
• Procedural memory examples: tying shoes, driving, pumping gas—initially effortful, later automatic with practice.
• Priming examples:
• Word-framing task: given contextual cues can bias the first word you think of (e.g., soap vs. soap-related words, which can lead to thinking of soup when preceded by related cues).
• Real-world priming: movie theater concessions cues (popcorn, drinks) prime behavior (buying snacks).

Memory problems and amnesia: two major types

• Retrograde amnesia: loss of memories from before the onset of amnesia (past memories affected).
• Anterograde amnesia: inability to encode new memories after onset (forming new memories impaired).
• Prevalence: anterograde amnesia is more common than retrograde amnesia.
• Example references discussed:
• Clyde Waring (example video): encoding difficulties with short-term/long-term memory and amnesia context.
• Classic film examples discussed to illustrate retrograde vs. anterograde memory loss: The Notebook (retrograde), Memento (anterograde), Finding Nemo (Dory’s episodic memory issues—labelled more as anterograde-like issue in the film), 50 First Dates (anterograde amnesia portrayal).
• Bourne Identity: common media portrayal of generalized amnesia; patchy accuracy for real-memory processes (generally exaggerated in films).
• Real-life case: HM (hippocampus removed in a bilateral surgical intervention for epilepsy)
• Result: mild retrograde amnesia and severe anterograde amnesia.
• Experiment: mirror-drawing task (drawn while viewing a reflection) showed intact procedural memory despite explicit memory impairment.
• Conclusion: the hippocampus is critical for explicit memory formation/recall; implicit memory, especially procedural memory, can remain relatively intact without the hippocampus.

The HM case study: implications

• Demonstrates dissociation between explicit and implicit memory systems.
• Suggests that some memory tasks rely on different brain regions; explicit memory relies on hippocampal/temporal lobe structures, while procedural memory relies on other areas (e.g., basal ganglia, cerebellum).
• Practical takeaway: intact implicit memory can support learning and skill improvement even when explicit recall fails.

Eyewitness testimony and memory malleability

• Eyewitness testimony is not as reliable as commonly assumed; memory can be distorted by post-event information.
• Brain Games video and Elizabeth Loftus demonstration emphasize memory malleability and the influence of questioning language.
• Core concepts:
• Unconscious transference: witnesses may recognize someone they saw nearby as the perpetrator, creating a false memory of recognition.
• Misinformation effect: information acquired after an event can contaminate or alter memory of the event itself.
• Planting false memories: through a deliberate manipulation of witnesses’ exposure to misinformation (as shown by Loftus and colleagues).
• Loftus’ misinformation effect: classic speed-estimate study
• Procedure: participants watch a car crash video; later asked to estimate speed with different verb prompts: "smashed into" vs. "hit" vs. "contacted".
• Result: higher speed estimates with stronger verbs (e.g., smashed) than with milder verbs (e.g., contacted).
• Forensic implications: eyewitness certainty does not reliably predict accuracy; confidence can be influenced by suggestive questions and post-event information.
• Real-world concerns:
• The correlation between confidence and accuracy is weak to modest.
• The impact of stress, weapon focus, and age (children especially) reduces accuracy; children are particularly susceptible to suggestibility and the influence of authority figures.
• Unconscious transference example through a staged lineup in the video: witnesses could misidentify a suspect due to familiarity with a person present at the scene but not the perpetrator; later manipulations could create a false memory of recognition.
• Implications for legal systems: caution in relying solely on eyewitness testimony; procedures to minimize misidentification include double-blind lineups, unbiased instructions, and separate testing to avoid cross-contamination of memory.

Misinformation and its study in memory science

• Core finding: information presented after an event can distort memory for the event itself.
• Classical experiment design (Loftus) to demonstrate misinformation effect:
• Participants view a crash video, then receive leading questions with verbs that imply different speeds; memory reports vary by wording even though the initial video was identical.
• Real-world connection: investigators should carefully elicit information; avoid leading questions; understand the power of language and suggestion on memory recall.

Memory forgetting and interference as forgetting mechanisms

• Interference is a key forgetting mechanism; two main types discussed:
• Proactive interference: old information interferes with the retrieval of new information.
  • Everyday examples discussed in class:
  • Year change: after the calendar flips to a new year, you might forget to use the new year; write 2024 when you mean 2025.
  • Password changes: you might keep entering the old password and forget the new one.
  • Language learning apps (Duolingo) where previously learned material interferes with learning new material (e.g., Spanish vs. Norwegian).
• Retroactive interference: new information interferes with the retrieval of older information.
  • Everyday examples discussed:
  • Difficulty recalling a person’s identity (e.g., who a pictured person is) after seeing a new set of information or a new set of items; or forgetting earlier facts after encountering new material (e.g., Wilhelm Watts case example).
  • General point: new information can overwrite or obscure older memories, particularly when the older memories are not well rehearsed.
• Practical study tip: relate interference concepts to personal experiences to deepen understanding and improve recall.

Bottom-line memory takeaway from the lecture

• Explicit and implicit memory are distinct systems with different brain substrates and behavioral manifestations.
• Amnesia can selectively impair explicit memory while preserving implicit memory, illustrating dissociation between memory systems.
• Eyewitness memory is fallible; memory can be distorted by misinformation, suggestive interviewing, and social dynamics such as confidence and certainty.
• Interference (proactive and retroactive) is a common cause of forgetting; everyday examples can make these concepts concrete.
• Post-lecture practice: connect concepts to previous lectures and foundational principles (e.g., hippocampus role, memory consolidation, retrieval processes) and real-world relevance (education, law, advertising).

Ethical, philosophical, and practical implications highlighted in the content

• Forensic and legal implications: misidentification and wrongful convictions due to flawed memory require careful lineup procedures and awareness of memory malleability.
• Marketing and advertising: priming and environmental cues can subtly steer behavior and choices, raising questions about manipulation and autonomy.
• Education and knowledge transfer: aligning study practices with how memory works (e.g., spaced repetition, deliberate practice) can improve retention and reduce forgetting.
• Media portrayal vs. scientific reality: popular films often depict memory phenomena (e.g., complete memory wipe in Bourne) inaccurately; educational media should emphasize evidence-based understanding.

Quick study prompts (from the session)

• Top Hat-style recall question: Which subtype explains forgetting how to ride a bike after four years away? Answer: Procedural memory (motor skills and habits).
• Short reflection prompts for memory study: give real-life examples of proactive and retroactive interference from personal experience; consider how eyewitness testimony could be improved in real-world settings.

Key formulas and notations (for quick reference)

• Long-term memory decomposition:
• LTM = E  I
• E = S  Ep
• I = Pr  Pm
• where
  • E = Explicit memory, I = Implicit memory
  • S = Semantic memory, Ep = Episodic memory
  • Pr = Procedural memory, Pm = Priming
• Amnesia types (definitions):
• Retrograde amnesia: loss of memories from the past (before onset)
• Anterograde amnesia: inability to encode new memories after onset
• Interference definitions:
• Proactive interference: old information interferes with new information retrieval
• Retroactive interference: new information interferes with retrieval of old information
• Misinformation effect (conceptual): information acquired after an event can distort memory of the event itself

References and anecdotes cited in class (for context during study)

• William Eilish (example of semantic knowledge)
• HM (Henry Molaison) case study: hippocampal involvement in explicit memory and preservation of procedural memory
• Loftus (misinformation/memory distortion; eyewitness testimony)
• Misinformation verb-speed study: smashed vs hit vs contacted
• Popular film examples discussed for memory themes: The Notebook (retrograde), Memento (anterograde), Finding Nemo (Dory’s memory issues), 50 First Dates (anterograde), Bourne Identity (amnesia depiction)

How to connect to broader course themes

• Biopsychology: how brain structures (e.g., hippocampus) support different memory systems
• Cognitive psychology: how memory encoding, storage, and retrieval interact with perception and attention
• Social/legal psychology: how memory malleability affects eyewitness testimony and the justice system
• Real-world application: adapting study strategies and critical Thinking about memory reliability in everyday life and media