Cognitive Processes PSY 334 Chapter 7 Human Memory: Retention and Retrieval
What is Forgetting? Do memories still exist in mind when we cannot remember? Penfield stimulated areas of the brain and got reports of recall from childhood. No way to check the accuracy of reports. Nelson some savings are evident even when subjects cannot remember items: Savings found with recall (78% unchanged, 43% changed) and recognition (34% & 19%).
Brain Areas Important to Memory
The Retention Function Wickelgren studied the retention function: Performance is a function of delay. Log (d) = A b log T Where: T is delay, d is performance (memory strength). Power law of forgetting -- power function becomes linear when plotted on log-log scales.
Power Law of Forgetting
Rate of Forgetting Retention function shows diminishing loss (forgetting) with delay. Theory of short-term memory predicts sharp drop-off followed by stable memory. Since all retention functions are like this, there is nothing special about short-term memory compared to long-term memory. Practice postpones the point of decay.
Long-Term Retention Bahrick studied retention of English- Spanish vocabulary over 50 years. Substantial practice effect. Slow decline after 3 yrs. Drop-off at end due to physical aging. Barnes decrease in long-term potentiation with delay. Mirrors retention function. Decay theory of forgetting LTP changes.
Bahricks Retention of Spanish Notice that retention only drops off at the end when subjects are 65+ in age.
Decay Decline in LTP
Interference Interference paradigm two groups defined: Experimental group learns new associations for previously learned list Control group learns entirely new list Typically the experimental group does worse after a delay. Does this mean that it is difficult to maintain multiple associations?
Typical Interference Experiment A-D ExperimentalC-D Control Learn A-B Learn A-DLearn C-D Test A-B A-D produces more interference than C-D
Fan Effect There is a limit to how much activation can spread within a network: The more associations, the less activation can spread to any particular structure. Anderson fan effect: Recognition time increases with the number of facts about a person and a location (e.g., lawyer, church). The brain works harder with high fans.
Andersons Experiment Mean Recognition Time for Different Numbers of Sentences 12 11.111.17 2 1.22
Preexisting Memories Does knowledge brought into an experiment interfere with new learning? Lewis & Anderson facts about Napoleon: Fantasy facts learned during experiment True facts from the real world False facts not studied in experiment and not true in the real world Fan effect occurs with all three fact types
Interference from Preexisting Facts
Interference vs Decay Less forgetting during sleep than when awake. Occurs because material is retained better when learned at night. Night is period of highest arousal. Forgetting functions may reflect interference from unknown sources. Decay theories do not specify any mechanism for decay.
Effects of Redundancy Interference occurs only when learning multiple memories that have no relationship to each other. Bradshaw & Anderson compared relevant and irrelevant fact learning: Irrelevant facts interfere. Relevant facts aid memory compared to single fact learning.
Relevant vs Irrelevant Information Immediate Recall % Recall at 1 week % Single fact9262 Irrelevant facts8045 Relevant facts9473
Retrieval and Inference Much of memory is inference at the time of recall not actual retrieval of facts. Bransford et al. -- inference can lead to incorrect recall: Turtles resting on or beside a log and a fish swam beneath them. Subjects were most confused by test sentences whose meaning was implied by the studied sentences (beneath it).
Carol Harriss Story Carol Harris was a problem child from birth. She was wild, stubborn, and violent. By the time Carol turned eight, she was still unmanageable. Her parents were very concerned about her mental health. There was no good institution for her problem in her state. Her parents finally decided to take some action. They hired a private teacher for Carol.
Inference-Based Intrusions Sulin & Dooling subjects add details not present during learning: Carol Harris vs Helen Keller She was deaf, dumb and blind. 5% Carol Harris but 50% Helen Keller subjects falsely recognized the sentence. Inferences are made at test-time. More inferential errors occur with delay.
Plausible Retrieval Reder much of recall is plausible inference not actual recall. Darth Vader inferred to be evil, not remembered to be evil. Heir to hamburger chain story subjects asked to recall exact details and make plausible inferences. After a delay, plausible inference is faster and does not decay as much as exact memory, with no fan effect.
Plausible Retrieval after a Delay
Inference and Elaboration Elaboration leads to more inferences. Information added as a theme to a story results in better recall of studied material and more inferences (Nancy & the doctor). Intruded inferences are not necessarily errors but help guide our thinking and behavior. Listerine court case false inferences, not just false statements, not permitted.
Memory Errors When exact memory is needed, inferences and reconstructive processes can be misleading. Loftus -- additional details and suggestion can change what is recalled. John Deans recall vs what Nixon recorded gist was right but not details. False memory syndrome memories that never happened can be planted.
Deese-Roediger-McDermott False Memory Paradigm Participants study lists of words: Thread, pin, eye, sewing, sharp, point, prick, thimble, haystack, thorn, hurt, injection, syringe, cloth, knitting Bed, rest, awake, tired, dream, wake, snooze, blanket, doze, slumber, snore, nap, peace, yawn, drowsy Later shown 3 types of words: True (sewing, awake), False (needle, sleep), New (door, candy) Participants accept 88% of true words & 12% of new, but also accept 80% of false words.
False Memories and the Brain The parahippocampus retains the sensory experience of seeing the word. The hippocampus extracts and stores the meaning.
Context Effects Recall is better if the physical context during learning is also present during testing. Experimenter clothing, setting. Under water. Eich suggests that context effects depend on integrating context and the material to be learned.
Mood Congruence Bower et al. hypnotized subjects and induced positive or negative mood. Recall better if hypnotized into the same mood during testing as during learning. Again, the effect may depend upon integration of mood with material learned. Mood congruence easier to remember memories congruent with the current mood.
State-Dependence Material is easier to recall if people return to the same emotional and physical state as during learning. Drinking some state dependence together with overall debilitating effect on memory. Marijuana and tobacco. Caffeine. Studying when not intoxicated is better.
Encoding Specificity The other items presented during learning provide a context too. Presentation of cues in as close to the original learning context aids recall. Encoding specificity principle: The probability of recalling an item depends on the similarity of its encoding at test to its original encoding at study.
Test of Encoding Specificity Watkins & Tulving: Study pairs of words Generate associates for words & indicate which were among studied words. Cued with first word of pair. 61% recall in cued task,