# Lecture 12: Memory: Forgetting and Reconstruction ## Introductory Psychology --- ## Learning Objectives By the end of this lecture, students will be able to: 1. Describe Ebbinghaus's forgetting curve and the major theories of forgetting 2. Distinguish between retrograde and anterograde amnesia 3. Explain how memories can be distorted and reconstructed 4. Evaluate the reliability of eyewitness testimony and recovered memories 5. Describe strategies for improving memory and reducing forgetting --- ## Lecture Content ### I. Forgetting: How and Why We Forget Hermann Ebbinghaus pioneered the scientific study of memory and forgetting in 1885 by memorizing lists of nonsense syllables and testing his retention over time. His research produced the now-famous forgetting curve, which shows that most forgetting occurs rapidly — approximately 50% of meaningless material is forgotten within the first hour, and roughly 70% is lost within 24 hours — after which the rate of forgetting levels off. Meaningful material is forgotten much more slowly. Even when conscious recall fails, Ebbinghaus demonstrated through his savings method that relearning material is faster than original learning, indicating that partial retention persists. ### II. Theories of Forgetting Several theories explain why forgetting occurs. Encoding failure means that information was never properly encoded in the first place — it is not true forgetting because the memory was never formed. The classic example is the inability to recall specific details of a penny despite having seen thousands of them. Storage decay, or trace decay theory, proposes that memories fade over time if they are not accessed or rehearsed. The physical memory trace, or engram, is thought to weaken with disuse. While the forgetting curve supports this idea, the theory is challenged by the persistence of very old memories and by instances of memories being recovered under certain conditions. Retrieval failure occurs when information is stored but cannot be accessed. The "tip of the tongue" (TOT) phenomenon — knowing you know something but being unable to retrieve it — is a common example. People in a TOT state can often recall partial information such as the first letter or the number of syllables. Retrieval depends on the availability of appropriate cues, consistent with the encoding specificity principle. Interference is one of the best-supported explanations for forgetting. Proactive interference occurs when old memories interfere with the retrieval of new information — your old phone number making it hard to remember your new one, for instance. Retroactive interference occurs when new learning disrupts the recall of older memories — learning Spanish vocabulary interfering with previously learned French. Sleeping after learning reduces retroactive interference because fewer new memories form to compete with the recently encoded material. Motivated forgetting encompasses both repression, Freud's concept of unconsciously pushing threatening thoughts out of awareness, and suppression, the deliberate, conscious effort to avoid thinking about something. While repression as a distinct mechanism has limited empirical support, research using the Think/No-Think paradigm has demonstrated that intentional suppression can impair later recall. A composite figure on forgetting. Panel A: Ebbinghaus's forgetting curve — a graph with time on the x-axis (0 minutes to 31 days) and percent retained on the y-axis (0-100%), showing rapid initial decline that gradually levels off. Panel B: A diagram comparing proactive and retroactive interference. For proactive: "Old learning (French)" blocks arrow to "New learning (Spanish)" with the label "old disrupts new." For retroactive: "New learning (Spanish)" blocks arrow back to "Old learning (French)" with the label "new disrupts old." Panel C: A flowchart showing the different types of forgetting: encoding failure (information never entered LTM), storage decay (memory trace fades), retrieval failure (memory exists but cannot be accessed), and interference (competing memories block access). ### III. Amnesia Retrograde amnesia is the inability to recall memories formed before a brain injury or event. It tends to be temporally graded — a pattern known as Ribot's law — meaning that recent memories are more vulnerable than remote ones, presumably because older memories have been more fully consolidated. Anterograde amnesia is the inability to form new long-term memories after a brain injury. The most famous case is patient H.M. (Henry Molaison), who, following hippocampal removal, could no longer form new explicit memories. He could, however, learn new procedural skills such as mirror tracing, demonstrating that implicit memory remained intact. He could hold information in working memory but could not transfer it to long-term storage. Patient Clive Wearing, who suffered severe anterograde and retrograde amnesia following viral encephalitis, retained his musical ability despite profound memory loss. Dissociative (psychogenic) amnesia involves memory loss without identifiable brain damage, often occurring after psychological trauma. Dissociative fugue, a related condition, involves sudden, unexpected travel away from home with confusion about one's identity. These conditions remain controversial and are difficult to distinguish from malingering. ### IV. Memory Construction and Distortion Memory is not a video recording but rather a reconstructive process. Sir Frederic Bartlett demonstrated this in 1932 in his book *Remembering*, in which participants retold the Native American story "War of the Ghosts." Over successive retellings, participants distorted unfamiliar details to fit their existing cultural schemas, and their accounts became shorter, more coherent, and more consistent with prior expectations. Schema-driven errors are common: we routinely fill in gaps in memory with information that is consistent with our preexisting frameworks. Source monitoring errors (or source amnesia) occur when a person remembers a piece of information but forgets where it came from, which can lead to unintentional plagiarism or false beliefs about the origin of ideas. The misinformation effect, extensively studied by Elizabeth Loftus, demonstrates that exposure to misleading post-event information can alter memories for the original event. In her classic study, participants who were asked "How fast were the cars going when they *smashed* into each other?" reported higher speeds and were more likely to falsely report seeing broken glass (which was not present) than participants asked about cars that "hit" each other. Post-event information becomes woven into the original memory trace. Imagination inflation refers to the finding that merely imagining an event increases one's confidence that it actually happened. False memories — detailed, confident recollections of events that never occurred — have been demonstrated in multiple paradigms. In the "lost in the mall" study, Loftus showed that participants could develop vivid memories of a fabricated childhood event after repeated suggestion. The DRM (Deese-Roediger-McDermott) paradigm reliably produces false recall: participants who study a list of related words (bed, rest, awake, tired, dream) frequently and confidently "remember" a critical lure word (sleep) that was never presented. A diagram illustrating the misinformation effect. Panel A: An eyewitness observes a car accident at an intersection with a yield sign. Panel B: During questioning, the interviewer mentions a stop sign (misinformation). Panel C: At later recall, the eyewitness now "remembers" a stop sign instead of the yield sign, with the original and altered memories shown side by side. Panel D: A bar graph showing Loftus's study results — participants asked "smashed" estimated higher speeds than those asked "hit," "bumped," "collided," or "contacted," with a second graph showing the percentage who falsely reported seeing broken glass across conditions. ### V. Eyewitness Testimony Eyewitness testimony is one of the most persuasive forms of evidence in courtrooms, yet research consistently shows it is often unreliable. Extreme stress and arousal narrow attention, producing the weapon focus effect, in which witnesses fixate on a weapon and fail to encode the perpetrator's face. The cross-race identification bias (other-race effect) means people are better at recognizing faces of their own racial group. Memory degrades rapidly with time, making details less accurate. Post-event contamination from discussions with other witnesses, media exposure, or suggestive questioning further distorts recall. Perhaps most important, confidence is not a reliable indicator of accuracy — highly confident witnesses can be wrong. The Innocence Project has used DNA evidence to exonerate hundreds of wrongfully convicted individuals, and eyewitness misidentification has been identified as the leading cause of wrongful convictions, playing a role in approximately 70% of DNA exoneration cases. Several procedural reforms have been recommended: the cognitive interview (which uses context reinstatement, unconstrained recall, changed perspectives, and varied temporal orders), double-blind lineup administration, sequential rather than simultaneous lineups (to reduce relative judgment), a warning that the perpetrator may not be in the lineup, and recording witness confidence at the time of identification. ### VI. The Recovered/False Memory Debate Recovered memories — recollections of traumatic events, often childhood abuse, that surface after years of apparent forgetting — have been the subject of intense debate. Some recovered memories may be genuine, since trauma can impair encoding or disrupt retrieval processes. However, others may be false memories created by suggestive therapeutic techniques such as hypnosis, guided imagery, repeated questioning, dream interpretation, and direct suggestion. The scientific consensus holds that both genuine recovered memories and therapist-induced false memories are possible, and that corroborating evidence is essential in any individual case. APA guidelines caution therapists against using suggestive techniques and against assuming that abuse occurred in the absence of independent evidence. ### VII. Strategies for Improving Memory Research has identified several evidence-based strategies for improving memory. Elaborative encoding — relating new information to what you already know — produces deeper, more durable memories. Distributed practice (spacing study sessions across time) is far more effective than massed practice (cramming). Retrieval practice (frequent self-testing) strengthens memory more than passive re-reading. Interleaving different topics during study enhances learning and transfer. Sleeping after study facilitates memory consolidation. Minimizing interference by studying different subjects in different contexts can reduce competition between memories. Mnemonic devices such as the method of loci, acronyms, the peg-word system, and visual imagery all provide organizational scaffolding that aids recall. Reducing multitasking is important because divided attention during encoding impairs memory formation. Finally, staying physically active supports hippocampal neurogenesis and overall memory function. A practical study guide infographic titled "Evidence-Based Strategies for Better Memory." Six panels arranged in a grid. Panel A: Spacing — a calendar showing study sessions distributed across multiple days vs. one long session the night before. Panel B: Retrieval practice — a student using flashcards and self-testing. Panel C: Elaboration — a web diagram connecting new concept to related prior knowledge. Panel D: Interleaving — three different colored problem types mixed together vs. blocked by type. Panel E: Dual coding — pairing a verbal description with a matching diagram. Panel F: Sleep — a timeline showing study followed by sleep followed by a test, with a brain icon consolidating during the sleep phase. ---