PSYCH 45 lecture 5/10/2011 Tuesday, May 10, 2011 9:30 AM Wagner: Memory Errors - False memory and Forgetting Continuing Understanding Imagination Inflation Source Memory Failures External Source Discrimination Person A vs. Person B TV vs. Web Heard vs. Seen Time 1 vs. Time 2 Internal Source Discrimination Thought vs. Did Reality Monitoring Imagined vs. Experienced Frontal Lobes and Source Memory Failures Study: presented 20 novel trivia facts The name of the dog on the Cracker Jacks box is Bingo. Retention Interval: 6-8 days Test: cued recall + source assessment What is the name of the dog on the Cracker Jacks box? If "Bingo", then" Can you tell me where you learned the answer? When was the last time you heard that information? What other situations might lead to false memories? False memory due to Memory for Gist? Source Confusion: DRM false memories due to reality monitoring / internal-external source failure Memory for gist: false remembrance based on similarity between current stimulus and central tendency/gist of past experiences Studies prototype, near, middle, and far images Logic: Not likely to self-generate the near, middle, and far images when presented with the prototype If memory for "gist", then false memory should depend on the similarity of novel images to the studied prototype Under some situations, false memory does not reflect source confusions False memory can occur when a new stimulus is similar to those we've previously encountered General conclusions about False Memory Memory is often a reconstructive process, and thus is prone to bias/distortion Multiple factors can foster conditions of increased false memory Source memory failures (imagination inflation) Judgments based on similarity/gist False recollection/recapitulation False memories can be nearly indistinguishable from true memories Phenomenologically (claim HC or to "remember") Neutrally (neocortical recapitulation) Why do we forget? Limited Capacity? Sometimes we don't learn in the first place? Decay: the weakening of memory traces due to the passage of time Cue-availability: forgetting occurs due to the loss of available retrieval cues Interference: retrieval is competitive, memories interfere with each other; disrupted target memory retrieval due to the presence of competing memories Suppression: retrieval of a target results in the suppression of a competitor The Forgetting Curve The forgetting function is negatively accelerated More and more delays yield smaller and smaller losses Why do we forget? Decay and Insufficient Retrieval Cues Retroactive Interference Negative effects of later learning on memory for earlier associations Proactive Interference Negative effects of earlier learning on memory for later associations Evidence for Interference: Cue-Overload (Fan Effect) The more information that is associated with a retrieval cue, the poorer the recall will be for any one piece of information Understanding Cue-Overload Relative-strength, global-matching model account Occlusion/Blocking Ratio Rule: p(recall) = [strength(cue, target i)]/[?strength(cue, target i) Assuming all targets have an equal associative strength with the cue, then the probability of recalling any item is: p(recall|4) = 1/4 p(recall|6) = 1/6 Retrieval Search and Global Matching Free Recall: P(recall Item j|Context x) = [Strength of Association btw Item j & Context x] / ?Association btw all Items and Context x Cued Recall: add Cue y ; multiply Cue y When remembering leads to forgetting Output Interference: the act of retrieval decreases the likelihood of being able to remember other associates of the cue. Interference Theory Blocking/occlusion Nothing happens to the target memory trace or its association to the cue Retrieval is strength dependent and competitive Forgetting due to response competition The cue allows a more dominant, non-target associated response to win the retrieval competition Alternative theory - Memory Suppression The retrieval of a competitor results in the direct suppression of another memory such that it is less accessible for recovery Possible Mechanisms for Competition-Driven Forgetting Retrieval practice phase Retrieval-Induced Forgetting (Suppression?) Retrieval of unpracticed category members is worse when other members of the category have been practiced Retrieval-induced forgetting occurs only for items that serve as competitors during retrieval phase The Adaptive Benefits of Forgetting The magnitude of forgetting is related to a decline in PFC cognitive control demands during repeated target memory retrieval Summary of Forgetting Mechanisms Factors contributing to forgetting Cue availability Trace delay Blocking/occlusion (interference) Retroactive and proactive interference Suppression Retrieval-induced forgetting
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