Memory Types, Forgetting, and Eyewitness Memory — Comprehensive Notes

Memory Types and Key Concepts

  • The lecture introduces sensory memory, short-term memory, and working memory as part of an upcoming class on long-term memory.
  • Emphasis on distinguishing explicit and implicit memory, and on how memory is studied and applied in real-world contexts (e.g., eyewitness testimony).

Sensory Memory

  • Sensory memory example: close your eyes and you can still see light for a fraction of a second.
  • This brief trace of sensory input is the sensory memory, which holds raw sensory information just long enough to be processed further.

Short-Term Memory and Working Memory

  • Short-term memory (STM) holds information temporarily and is the cognitive workspace used for conscious processing.
  • Working memory is the active portion of STM, involved in manipulating information (e.g., following procedures, mental calculation, planning actions).
  • An example mentioned: recalling a telephone number or following bicycle procedures involves short-term/working memory processes that may occur with varying levels of conscious effort.

Long-Term Memory: Explicit vs Implicit

  • Explicit memories require conscious effort to retrieve and recall. They include two main types:
    • Semantic memory: memory for facts and general knowledge.
    • Episodic memory: memory for personal experiences and events.
  • Procedural memory is a form of implicit (non-declarative) memory governing how we do things (skills and procedures like riding a bicycle or walking) that we perform without conscious recall of how we learned them.
  • Implicit memory includes memories that influence behavior without conscious awareness. It contrasts with explicit memory, which requires intentional retrieval.
  • Flashbulb memories: vivid memories for events, described as memories for events but not necessarily the personal experience of those events. These memories are unusually detailed and enduring, but their accuracy can be questioned.
  • The slides also mention priming and conditioning as topics reserved for discussion in the learning module.

Elaborating on Explicit vs Implicit Memory

  • Explicit memory (declarative) involves conscious recall of information.
  • Semantic memory holds general knowledge (facts, concepts).
  • Episodic memory holds episodes or personal experiences (time-stamped events).
  • Implicit memory (non-declarative) includes procedural memory (skills), as well as other memory effects like priming and conditioning, which do not require conscious recall.
  • The term "procedural memory" is used to describe learned actions and procedures that you can perform automatically (e.g., riding a bike) without actively recalling the steps every time.

Forgetting and Retention Over Time

  • A key graph described: at 100% initial recall, forgetting occurs rapidly after encoding. In the first hour, roughly 50% of the information is forgotten (i.e., memory retention declines quickly).
  • If information is remembered after the first hours, it tends to be retained longer, with possible retention through tens of hours, days, and even longer (e.g., remembering a number after 10 hours, 1 day, 2 days, 3 days and beyond).
  • The general pattern: forgetting is pronounced in the early hours and days after encoding; later forgetting happens more slowly, but can still occur.
  • Practical implication: eyewitness memory is highly time-sensitive. Interview timing affects recall accuracy; within 30 minutes to 4 hours after an event, memory may degrade significantly; after 15–20 days, differences in recall are less pronounced because the memories that remain are more stabilized.

Why Do We Forget?

  • The central question: why does forgetting occur?
  • Possibilities discussed:
    • Encoding not followed by rehearsal may lead to loss, but this view is challenged by evidence emphasizing interference rather than time alone.
    • If interference is avoided, forgetting could be reduced or absent; thus forgetting is not merely time passage but the intrusion of new information.
  • An everyday example given: learning a new lunch routine (or any new information) during a period where you don’t encounter related information may lead to better retention for the old information because there is less interference.
  • Two main types of interference causing forgetting:
    • Retroactive interference: newer information interferes with the recall of older information. Example: newer lunches or newer information getting in the way of remembering an older memory.
    • Proactive interference: older memories interfere with the acquisition or recall of new information (e.g., an old debit card code interfering with a new one).
  • A vivid analogy about doors: the mind’s memories can be like a door that previously closed from the outside; a new memory (e.g., how the door now closes from the inside) interferes with the old memory of closing it from the outside. This illustrates how old and new memories can conflict due to different contexts or retrieval cues.
  • The practical implication for real-world memory use: interference explains why people may remember old codes or numbers wrongly after new ones are introduced.

Eyewitness Memory and Interviewing

  • The practical aim in the speaker’s line of work: improving investigative interviewing to help eyewitnesses remember more accurate details.
  • Core premise: information is not erased from memory; memories can be influenced, enhanced, or distorted by the interviewing process if the right techniques are used.
  • The “computer analogy”: memories are like files saved on a computer; they can be stored, accessed, edited, or corrupted by new information and retrieval conditions. Files can be lost or altered, leading to false memories.
  • False memories: the creation of memories for events or details that did not occur, resulting from interference, post-event information, or suggestive questioning. These can range from minor details to full false narratives.
  • Key takeaway for eyewitness interviewing: use proper strategies to help the eyewitness access and recall information accurately, recognizing that memory is reconstructive and susceptible to interference and misinformation.
  • The instructor emphasizes the importance of recall: pay attention to cues and the word recall when discussing memory retrieval (the note ends with a prompt to focus on recall cues, though the sentence trails off).

Summary of Mechanisms and Connections

  • Memory architecture touched on here includes sensory memory, short-term/working memory, and long-term memory with explicit and implicit divisions.
  • Encoding strength and retrieval cues influence how well information is stored and later recalled.
  • Forgetting is driven not only by time but significantly by interference from other memories and new information (retroactive and proactive interference).
  • The accuracy of memories, especially in high-stakes contexts like eyewitness testimony, can be improved or degraded by interview techniques, the timing of retrieval, and external information.
  • There is a continuous theme of memory being constructive and malleable, not a perfect recording of events; learning, memory storage, and recall are dynamic processes influenced by context, time, and cognitive strategies.

Notable Terms and Concepts to Remember

  • Sensory memory
  • Short-term memory (STM)
  • Working memory
  • Long-term memory
  • Explicit (declarative) memory
  • Implicit (non-declarative) memory
  • Semantic memory
  • Episodic memory
  • Procedural memory
  • Flashbulb memories
  • Priming
  • Conditioning
  • Forgetting curve / forgetting rate
  • Interference: retroactive vs proactive
  • Eyewitness memory and investigative interviewing
  • Computer analogy for memory and false memories
  • Recall (retrieval) cues and their importance in memory retrieval

Questions to Consider (for exam prep)

  • How do sensory memory, short-term memory, and working memory differ in duration and function?
  • What distinguishes semantic memory from episodic memory, and where does procedural memory fit in?
  • Why is forgetting faster in the first hours/days after encoding, and what role does interference play?
  • Define retroactive and proactive interference with examples.
  • How can interviewing techniques influence eyewitness memory, and why might false memories arise?
  • What is the role of retrieval cues in memory recall, and how does the computer analogy illustrate memory reconstruction?

Note on the Speaker’s Emphasis

  • The lecturer emphasizes that memory is not a static recorder; it is subject to decay, interference, and reconstruction.
  • The discussion connects theory to practical applications in law enforcement and investigative interviewing, highlighting ethical and practical implications of memory research.
  • The final prompt to focus on recall suggests that the act of retrieval and the cues used are central to understanding and measuring memory performance.