2.7

The Function and Necessity of Forgetting

• Adaptive Purpose of Forgetting:

  • Complete retention is as debilitating as complete amnesia, as expressed by William James (1890, p. 680): "If we remembered everything, we should on most occasions be as ill off as if we remembered nothing."
  • Forgetting irrelevant, out-of-date, or trivial information—such as old locker combinations, former phone numbers, or delivered restaurant orders—frees cognitive capacity for critical information (Murphy & Castel, 2021; Nørby, 2015).
  • Discarding negative memories is essential for maintaining emotional and mental well-being (Stramaccia et al., 2020).

• Hyper-Retention and Highly Superior Autobiographical Memory (HSAM):

  • Solomon Shereshevsky: A 1920s Russian journalist studied by Alexander Luria (1968).
    • Could memorize long sequences of random data or long passages of Dante's Inferno in Italian without speaking Italian (Johnson, 2017).
    • Suffered from a conscious mind dominated by a junk heap of memories, making abstract thinking, generalizing, organizing, and summarizing narrative gists extremely difficult.
  • Jill Price: Studied by researchers at the University of California, Irvine (McGaugh & LePort, 2014; Parker et al., 2006).
    • Possesses Highly Superior Autobiographical Memory (HSAM), allowing near-perfect recall of daily life events since age $14$
    • Describes her memory as a "running movie that never stops… nonstop, uncontrollable, and totally exhausting."
    • Mind fills with details that most people ignore and discard (e.g., exact clothing worn on a first date or the day of the week of a childhood restaurant visit) that permanently remain in storage (Frithsen et al., 2019; Patihis, 2016).
  • Neurological Findings: Worldwide, approximately $60$ individuals with HSAM have been identified; neuroimaging reveals enlarged brain regions and heightened neural activity within memory centers (Dutton, 2018; Santangelo et al., 2020).

• Information Filtering:

  • Human information processing constantly filters, alters, and drops sensory inputs across stages of encoding, storage, and retrieval.

Amnesia and the Two-Track Mind

• Types of Amnesia:

  • Anterograde Amnesia: The inability to form new conscious explicit memories following neural trauma or surgery, while past memories stored prior to the damage remain intact.
  • Retrograde Amnesia: The inability to retrieve past information stored in long-term memory prior to neural injury.

• Clinical Case Studies:

  • Henry Molaison (H. M., 1926–2008):
    • Surgeons removed major portions of his hippocampus to stop persistent seizures, resulting in severe disconnection of the remaining hippocampus from other brain regions (Annese et al., 2014).
    • Lived for $55$\,years unable to form new explicit memories.
    • Retained normal intelligence, short-term memory capacity of approximately $30$\,seconds, and pre-surgery memories, but could never name current public figures or identify neuroscientist Suzanne Corkin, who worked with him from 1962 until his death (Corkin, 2005, 2013; Ogden, 2012).
  • Patient "R":
    • Exhibited a post-surgical personality shift from introversion to extraversion, yet retained his pre-surgical self-concept as an introvert when completing self-report personality inventories (Garland et al., 2021).
  • Jimmie:
    • Documented by Oliver Sacks (1985); developed severe anterograde amnesia from alcohol-related brain damage.
    • Possessed no conscious memory or sense of elapsed time beyond 1945. Stated his age was $19$ and panicked when shown his aging reflection in a mirror, though immediate distraction by children playing baseball fully erased his panic.
    • Exhibited intense wonder when shown a National Geographic photograph of Earth taken from the Moon, treating it as an astounding futuristic feat.

• Dissociation of Explicit and Implicit Memory Systems:

  • Amnesic patients (including H. M., Jimmie, and individuals with Alzheimer's disease) lose explicit declarative memory processing while automatic implicit nondeclarative memory processing remains functional (Lustig & Buckner, 2004).
  • Implicit Skill Acquisition:
    • Patients can learn nonverbal procedural skills, including mirror-tracing, navigating unfamiliar spaces (e.g., finding a bathroom), solving complex jigsaw puzzles, reading mirror-image text, and mastering procedural job skills (Schacter, 1992, 1996; Xu & Corkin, 2001).
    • They can be classically conditioned and quickly locate hidden figures (e.g., Where's Waldo? pictures) upon re-exposure.
    • They execute these skills efficiently without any conscious awareness or explicit memory of having practiced or learned them (Shapin, 2013).

• Methodological Limit of Case Studies:

  • Case studies offer deep descriptive detail on rare individual conditions, but critical scientific thinking requires recognizing that their generalizability to broader populations is inherently limited.

Mechanisms of Forgetting

• Encoding Failure:

  • Sensory information that is not actively attended to or processed fails to encode into long-term storage and can never be retrieved.
  • C. S. Lewis (1967) observed that humans ignore approximately $\frac{9}{10}$ of sensory input received every second.
  • Unencoded short-term memory items are lost through displacement as incoming information exceeds working memory limits (e.g., dialing sequential phone numbers displaces earlier numbers).
  • Age-Related Effects: Neural structures active during encoding in young adults display reduced activation in older adults, contributing to age-related memory decline (Grady et al., 1995).
  • Selective Attention Deficits: In a sample of $85$ UCLA students (including $52$ daily Apple product users), only $1$ participant accurately drew the Apple computer logo, demonstrating that repeated exposure without encoding effort fails to produce stable memories (Blake et al., 2015).

• Storage Decay:

  • Gordon Bower (1973) noted that memory degradation begins immediately following learning.
  • Ebbinghaus Forgetting Curve: Hermann Ebbinghaus (1885) memorized lists of nonsense syllables (e.g., YOX, JIH) and tested retention across intervals from $20$\,minutes to $30$\,days.
    • Found that forgetting is initially rapid and exponentially steep, then plateaus over time (Wixted & Ebbesen, 1991).
  • Spanish Vocabulary Retention: Harry Bahrick (1984) evaluated retention of high school and college Spanish across $50$\,years.
    • Retention dropped sharply over the first $3$\,years post-graduation, but vocabulary retained after $3$\,years remained stable $25$ to $50$\,years later.
  • Physical Storage Basis: Decay reflects the gradual fading or degradation of physical neural memory traces.

• Retrieval Failure:

  • Inaccessible long-term memories result from insufficient or missing retrieval cues rather than physical trace destruction.
  • Tip-of-the-Tongue (TOT) Phenomenon: A temporary inability to access stored information, occurring with increased frequency in older adults (Abrams, 2008; Salthouse & Mandell, 2013). Fluent deaf signers experience a parallel "tip-of-the-fingers" phenomenon (Thompson et al., 2005).
  • Retrieval Cues: Cues that match internal visualizations (e.g., the cue word "shark") access encoded sentences ("The fish attacked the swimmer") more effectively than the original literal sentence components (Anderson et al., 1976).

• Interference:

  • Proactive Interference (Forward-Acting): Prior learning disrupts the recall of newly acquired information (e.g., an old combination lock sequence preventing recall of a newly assigned combination).
  • Retroactive Interference (Backward-Acting): New learning disrupts the recall of previously stored information (e.g., learning new lyrics sung to an established melody interfering with recalling the original lyrics).
  • Sleep Protection: Information presented in the hour prior to sleep suffers minimal retroactive interference because interfering waking events are minimized (Mercer, 2015).
  • Jenkins & Dallenbach (1924) Study: Participants who slept immediately after learning nonsense syllables retained significantly more items than those who stayed awake and engaged in daily activities. Demonstrates that forgetting is largely driven by active interference rather than passive temporal decay.
  • Sleep Caveats: Information presented in the final seconds before falling asleep is not encoded (Wyatt & Bootzin, 1994), and playing audio recordings during sleep produces no conscious memory retention (Wood et al., 1992).
  • Positive Transfer: Previously learned information facilitates the learning of new material (e.g., knowledge of Latin assisting the acquisition of French vocabulary).

• Motivated Forgetting and Repression:

  • Self-Serving Memory Revision: People systematically adjust past memories to preserve self-esteem and self-concept.
  • Individuals informed of the health benefits of frequent toothbrushing recalled brushing significantly more often over the preceding $2$\,weeks than control participants (Ross et al., 1981).
  • In a real-world study of household consumption, family members estimated eating a combined total of $89$ cookies out of an actual $160$, demonstrating systematic self-serving underestimation.
  • Freudian Psychoanalytic Theory: Sigmund Freud posited repression as an automatic defense mechanism that banishes anxiety-provoking or unacceptable thoughts, feelings, and memories into the unconscious ego-defense system.
  • Modern Scientific Consensus: Memory researchers conclude that repression rarely, if ever, occurs.
  • Trauma and Memory: Stress hormones released during traumatic events heighten focus and consolidate emotional memories (Quaedflieg & Schwabe, 2017), leading to persistent, intrusive memories rather than amnesia (Marks et al., 2018).
  • Flight AT236 Study: Margaret McKinnon evaluated $15$ survivors of a transatlantic flight that lost all engine power and prepared for an ocean landing before safely grounding in the Azores. Four years post-event, all survivors displayed vivid, detailed, and robust memories of the trauma without evidence of repression (McKinnon et al., 2015).

Memory Construction and Distortion

• Reconsolidation and Constructive Memory:

  • Nearly two-thirds ($64\%$) of the public holds the misconception that human memory records events accurately like a video camera (Simons & Chabris, 2011).
  • Memories are constructed at retrieval by combining actual stored traces with current expectations, beliefs, and post-event details.
  • Reconsolidation Process: Replaying a memory renders it malleable, replacing the original trace with a modified version upon re-storage (Hardt et al., 2010; Elsey et al., 2018). Joseph LeDoux (2009) noted: "your memory is only as good as your last memory. The fewer times you use it, the more pristine it is."
  • Loftus Demonstration: Psychologists presented with facial lineups selected altered target faces on subsequent tests, replacing their original memories through reconsolidation (Loftus, 2012).
  • Clinical Applications: Researchers use administration of propranolol, electroconvulsive shock, or targeted distracting imagery during memory retrieval to disrupt reconsolidation and extinguish fear responses associated with trauma (Phelps & Hofmann, 2019; Scully et al., 2017; Treanor et al., 2017).

• Misinformation Effect:

  • Exposure to subtle misleading post-event information leads individuals to confidently misremember witnessed events (Anglada-Tort et al., 2019; Loftus et al., 1992).
  • Approximately $50\%$ of individuals are susceptible to misinformation distortions across experimental paradigms (Brewin & Andrews, 2017; Scoboria et al., 2017).
  • Loftus & Palmer (1974) Experiment: Participants viewed a traffic collision video clip.
    • Participants asked "About how fast were the cars going when they smashed into each other?" gave higher speed estimates than those asked with the verb "hit."
    • One week later, participants in the "smashed" condition were more than twice as likely to falsely recall seeing broken glass (despite no broken glass existing in the film).
  • Behavioral Effects: Misinformation alters subsequent behaviors; suggesting to university students that they became ill from spoiled egg salad as children significantly reduced their consumption of egg salad $4$\,months later (Geraerts et al., 2008).
  • Misattributing Familiarity: Due to general familiarity, many Americans misremember historical figures such as Alexander Hamilton as U.S. presidents (Roediger & DeSoto, 2016).

• Imagination Inflation:

  • Visualizing non-existent events creates false memories. Viewing digitally manipulated album photos (e.g., adding a child to a hot-air balloon ride) caused children to generate rich, highly confident false memories that expanded in detail over time (Strange et al., 2008; Wade et al., 2002).
    • Independent Variable: Type of photograph presented (altered vs. unaltered).
    • Dependent Variable: Frequency, confidence, and richness of false memory reports.
  • $39\%$ of surveyed adults report explicit memories from age $2$ or younger, which are developmental impossibilities (Akhtar et al., 2018).
  • Approximately $\frac{1}{4}$ of university students report childhood memories they later identified as completely false (Foley, 2015; Mazzoni et al., 2010).

• Source Amnesia (Source Misattribution):

  • Attributing a memory, idea, or experience to an incorrect source while retaining the core informational content.
  • Child Development Example: Jean Piaget held a vivid lifelong memory of his nursemaid defending him from a kidnapper, which was revealed to be a false story invented by the nursemaid that Piaget had internalized.
  • Cryptomnesia: Unintentional plagiarism occurring when an individual misattributes an idea read or heard elsewhere to their own creative imagination.
  • Déjà Vu Mechanisms: An uncanny sense of repeated experience triggered when temporal lobe processing (generating feelings of familiarity) occurs slightly out of synchronization with hippocampal and frontal lobe processing (retrieving conscious details) (Cleary & Claxton, 2018; Urquhart et al., 2018).

• Distinguishing True from False Memories:

  • Subjective confidence, emotional intensity, and vividness do not differentiate real memories from constructed false memories (Schooler et al., 1986).
  • Deese-Roediger-McDermott (DRM) Paradigm: When presented with lists of semantically related words (e.g., candy, sugar, honey, taste), participants falsely recognize non-presented core gist words (e.g., sweet) $3$ out of $4$ times (Roediger & McDermott, 1995).
  • Social Contagion of Memory: Hearing peers construct false details leads listeners to misattribute the source and integrate those false details into their own memories (Roediger et al., 2001; Hirst & Echterhoff, 2012).

• Legal and Social Implications:

  • Wrongful Convictions: Out of $375$ individuals exonerated by post-conviction DNA testing in the United States, $69\%$ were convicted primarily on eyewitness misidentification (Innocence Project, 2020; Wells, 2020).
  • Other-Race Effect: Misidentifications across racial groups contributed to over $40\%$ of DNA exoneration cases (Innocence Project, 2020).
  • Hypnotic Refreshing: Hypnosis increases false memory production by introducing interviewer bias and leading questions.
  • Attitude Reconstruction:
    • Dating partners who remain in love reconstruct past impressions positively, whereas broken-up couples retroactively minimize their past affection (McFarland & Ross, 1987).
    • Individuals asked about their political opinions from $10$\,years prior recall past views as far closer to their current stances than their actual historical survey responses (Markus, 1986).
    • Students who wrote essays supporting tuition increases developed false memories of having supported the policy prior to writing the essay (Rodriguez & Strange, 2015).

Children's Eyewitness Reliability

• Vulnerability to Suggestive Interviewing:

  • Stephen Ceci and Maggie Bruck (1993, 1995) demonstrated that young children's memories are highly malleable under suggestive questioning.
  • Anatomical Doll Testing: When asked to indicate on anatomically detailed dolls where a physician examined them, $55\%$ of $3$-year-old children who had received routine, non-genital medical exams pointed to genital or anal areas.
  • Mousetrap Experiment: Preschoolers were repeatedly asked over $10$\,weeks: "Can you remember going to the hospital with a mousetrap on your finger?"
    • Upon being questioned by a new interviewer after $10$\,weeks, $58\%$ of preschoolers generated elaborate, highly detailed false stories about the fictitious event (Ceci et al., 1994).
    • Neither professional child interviewers nor the children themselves could reliably distinguish these false reports from authentic memories.
  • Susceptibility: Analysis of over $20,000$ eyewitness participants confirmed that child eyewitnesses regularly identify innocent suspects as perpetrators in lineup tasks (Fitzgerald & Price, 2015).

• Best Practices for Eliciting Accurate Recall:

  • Children provide accurate eyewitness descriptions when interviewed by a neutral party using unbiased, non-leading, age-appropriate language (Brewin & Andrews, 2017; Goodman, 2006; Wixted et al., 2018).
  • Maximum accuracy occurs during the initial interview, provided the child has not been subjected to prior suggestive discussions with adults (Holliday & Albon, 2004; Pipe et al., 2004).

Evidence-Based Memory Improvement Strategies

• Repeated and Spaced Rehearsal:

  • Utilize distributed practice across multiple study intervals rather than massed practice (cramming).
  • Retrieve target items at least $3$ times during study sessions before ending review (Miyatsu et al., 2018).
  • Production Effect: Actively speaking, writing, typing, or explaining material out loud produces vastly superior retention compared to passive silent reading (MacLeod & Bodner, 2017; Bisra et al., 2018; Forrin & MacLeod, 2018; Koh et al., 2018).

• Elaborative Encoding and Personal Meaning:

  • Build dense retrieval networks by forming explicit personal associations, organizing concepts hierarchically, and drawing visual representations (Fernandes et al., 2018).
  • Follow William James's (1890) principle: "Knit each new thing on to some acquisition already there."

• Contextual Cue Activation:

  • Re-create the physical context and emotional state of original learning (context-dependent and state-dependent memory cues) to trigger associative pathways.

• Mnemonic Utilization:

  • Employ structured mnemonic systems, visual imagery narratives, chunking, and acronyms (e.g., using "Never Eat Soggy Waffles" for cardinal directions).

• Interference Reduction:

  • Schedule study sessions immediately prior to sleep to prevent retroactive interference. Avoid studying subjects prone to mutual interference back-to-back (e.g., sequential study of French and Spanish).

• Sleep Optimization:

  • Maintain adequate sleep schedules to allow the brain to process, reorganize, and consolidate long-term memories (Cousins et al., 2020; Leong et al., 2020).

• Active Self-Testing:

  • Capitalize on the testing effect to combat recognition overconfidence. Practice active recall through blank-page outlining, flashcard retrieval, defining terms prior to checking definitions, and completing practice assessment questions.