5/4: False Memories.pdf

5/4: False memories Recognizing the past: recollection and familiarity Unitary view: single source of information Weigh amount of evidence we have, above criterion = recollection, below criterion = familiar Dual process theories 2 different signals for recollection and familiarity Encoding Hippocampal activation during is predictive of- Recollection, but not familiarity Activation of cortex around hippocampus during learning is predictive is- Familiarity, not recollection fMRI: REcollection at retrieval Remember/know test Two-step decision: Recognize that it's old or think it's new If it's old, do you remember it, or do you just think it's familiar Remember = recollection of details that surrounded the object that was studied Know = don't remember the details, but have a strong sense of familiarity Different brain activation when people say they remember it vs. know it Self-reports as a proxy for if items are being remembered with recollection or familiarity Brain activation Hippocampus is only active during correct remembers Hippocampus doesn't differentiate for false alarms or remembers Repetition suppression and item familiarity Decrease in firing rate of a neuron after repeated exposure MTL cortex Novel > repeated ~25% of neurons single trial Hippocampus ~1% of neurons Stimulus-context conjunctions How is familiarity signaled? Graded repetition effect on MTL 12 Neural responses decrease to familiar stimuli at retrieval match between current stimulus and memory trace of past stimulus/stimuli Evidence for central tenets of relational memory theory Cortex learns about items themselves Hippocampus is involved with relational memory binding False memory: Distortions and errors in mind and brain Recovered memory syndrome An individual can have a memory encoded and consolidated, but not aware/reactivate memory At some point, given the right retrieval cues, the individual remembers Often associated with child abuse George Franklin Evidence convicting him of murdering his daughter's childhood friend This was the ONLY evidence There wasn't any more new information in her memory. Her info was the same as those that were in newspapers Some of her facts were the same facts that the newspapers misreported Memory and the law in India They have a brain based method that tells them if people actually saw an event going on There are instances of recovered memories, in which you remember something you haven't thought about for a long time Can you implant whole, large-scale false memories? Edward Daily and the No Gun Ri Massacre Korean War vet said he was present for a civilian massacre During the moment when the massacre was occurring, he was stationed elsewhere Memory error where he had heard about it from soldiers who actually were present Failed to recall the source, and over time came to believe that he was actually there Hillary Clinton and Bosnia case Implanting false memories in the lab Obtain a few facts from friends/family and embed them in a false memory Lost in a shopping malll Generate details about false event Say that they spoke to friends/family Subjects recalled 68% of true events and 29% of false events When they called them to debrief, some subjects clung to false memory, even when they were told it didn't happen Spilling punch on bride's dress Can someone be confident in a memory that is not real? Deese-Roediger/McDermott (DRM) Paradigm Have a bunch of words around a theme Critical lure- stimuli that weren't actually studied, but are semantically related Higher probability of recognizing and generating these items Results Confidence ratings HC = high confidence Very few high confidence false alarms May high confidence hits Often give high confidence endorsements of critical lures LC = low confidence Remember/know ratings Give remember responses with a similar probability for studied and critical lure items Claim to recollect and experience what didn't occur Can easily have a false memory when things are similar Can have very confident recollections Can real memories be altered? Can memory for an event that actually occurred be altered/changed by the things that occur in between that event and the final probe? Misinformation effect In eyewitness testimony, the memory is being probed repeatedly If each of the acts of retrieval are powerful learning events, if the way we cue the memory is done in a manner that either inserts false information or probes memory in a biased manner, does the report of the event change, and does the actual memory get altered? Original event (watching slides of traffic accident) Following event, memories are probed Neutral probes = questions don't insert false information, not does the question re-present true info MIdleading info = question gets some facts wrong; question itself is bringing up false information Final test of memory Competition between two memory traces: actual memory, and misinformation Sometimes we can become led astray and endorse false information The suggestions effect Retrieval is a reconstructive act that includes the interplay between what was originally learned and what our cues are Bias between features Study: watch a film of a car accident Test Eyewitness questioning using different language "About how fast were the cats going when the two cars _______ each other?" Contacted- 32 mph Hit- 34 mph Bumped- 38 mph Collided- 39 mph Smashed- 41 mph A week later, Ss in the "smashed" condition were more likely to (incorrectly) report broken glass Can imagination be mistaken for reality? Imagination inflation If someone's confident that something occurred, does the confidence increase if you provide them details or if you have them create a mental image Imagination makes them remember it more Can we get a neural record for the perceptual detail present? Relationship between perceptual detail and likelihood of remembering? See word, picture of that word, another word, then supposed to imagine the referent Test Auditory cues Sees whether or not they remember being presented a picture of the referent Results Probability of remembering seeing a picture = word + picture > word only > new If you listen in on occipital and parietal lobes, the greater the neural response during the active imagery, the higher the probability that they'll think they saw the picture Rich vivid imagery reates a memory that resembles the contents of a real memroy During retrieval, the reactivation of these rich details is falsely attributed to having actually seen the stimulus The closer the imagination gets to a perception, the higher the likelihood of confusion Sources memory failures Reagan had memory of liberating a concentration camp, but really he was in Hollywood External source discrimination = trying to decide where you got a memory Internal source discrimination = if you thought something or if you actually did something Neurobiology of source memory PFC Individuals who have damage might demonstrate normal memory for facts, but higher probability of failure to know where facts cam efrom Important for interrogating memories Figuring out where they encountered the info Janowsky study Presented with 20 novel trivia facts Retention interval: 6-8 days Test: cued recall + source assessment If they can recall it, tell them where they heard it Results Misreporting where they learned the fact a week later Misreporting where they learned the fact a week later What situations might lead to false memories? Lizz Fay Untitled