Chapter 6 Forgetting. Bodrov Alexey

Outline Introduction Consolidation Theory Interference Theory Release from proactive interference (PI) Relative Distinctiveness Discrimination problem Conclusions Biointelligence Lab http://bi.snu.ac.kr

Introduction Marcus Tullius Cicero We are told that the famous Athenian Themistocles was endowed with wisdoms and genius on a scale quite surpassing belief; and it is said that the certain learned and highly accomplished person went to him and offered to impart to him the science of mnemonics, which was then being introduced for the first time; and that when Themistocles asked what precise result this science was capable to achieving, the professor asserted that it would enable him to remember everything; and Themistocles replied that he would be doing him a greater kindness if he taught him to forget what he wanted than if he taught him to remember. Marcus Tullius Cicero Biointelligence Lab http://bi.snu.ac.kr

Consolidation Theory First prediction: Ebbinghause (1885) noted that the rate of forgetting is slowed when a period of sleep occurs between study and test. Third prediction: Quatermain, McEwen, and Azmitia (1972) tested this prediction using the same procedure (see second prediction), but they tested all animals 24hr, 48hr, 72hr after the ECS. Results: evidence of amnesia in those animals tested 24hr, 48hr after ECS, but no evidence of amnesia after 72hr. This directly contradicts the third prediction. So the weaker form appeared: Some biological changes may indeed affect an organism Second prediction: An experiment by Chorover and Schiller (1985). Placing a rat on a raised platform The animal stepped off the platform The rat received a mild foot shock (if the rat stayed nothing happened) After some period of time the rats was subjecting to electroconvulsive shock Chorover and Schiller varied the interval between the learning episode (stepping down) and administration of ECS. They estimated that consolidation is complete within 10s (this coincided nicely with conception of the duration of information in short term memory) Consolidation theory is not really a theory of forgetting but rather a theory of why information is not stored in a first place. 3 key predictions: 1) Memory should be better, then, following a rest period than following a period of activity. 2) Memory should be worse, then, following some event that prevent the consolidation. 3) If consolidation is prevented, the item should never be recalled because the essential storage phase was not complited. Biointelligence Lab http://bi.snu.ac.kr

Interference Theory John McGeoch was the “founder” of that theory. He divided interference into 2 parts: retroactive and proactive. The A-D learning does not erase the memories of the A-B learning. There is no loss of information, only a lapse in retrieving it. McGeoch identified 3 mechanisms that can cause interference: 1) Response competition 2) Altered stimulus conditions 3) Set Response competition occurs when two or more items are potential responses to a memory query. Experiment: Subjects learned to associate a series of items with cues, the A-B learning, and then “rested” for 30 min. Other groups had either 5, 10, 20, or 40 trials learning A-D paired associations. Conclusions from the experiment: The difference in recall between the control and experimental groups could not be attributed solely to competition from D items. Abernathy (1940) demonstrated the alternation of context. In his experiments the students who were tested in the same classroom they were taught in did better than students who were tested in a different classroom. Set can be thought of as a special version of context effects, with the subject using an inappropriate mind set. The typical example is failing to recognize a friend from a college when you happen to run out into a person during a visit home. McGeorge’s influence was so profound that no theories of forgetting from long-term memory propose decay as main explanation. Biointelligence Lab http://bi.snu.ac.kr

Release from proactive interference (PI) Experiment like Brown- Peterson’s was conducted (the difference is in switching from consonants to numbers for a half of subjects). Performance in the switched group was much better that in control group. Release from PI is equal to (x/y)*100 It was showed that change in materials was crucial, rather than the fact that one material is easier then another. The decay view cannot predict an increase in performance. Biointelligence Lab http://bi.snu.ac.kr

Relative Distinctiveness (1) Foundation of a theory: items will be well recalled to the extant they stand out or differ in some fashion from surrounding items. (If the item at position 6 of a 12-item list is red and all other items are black, it will be well recalled). Experiment: Brown-Peterson task. Distractive task – counting backwards for 10s/15s/20s. The proportion of items recalled correctly: 0.85, 093, 093 (first trial) and 0.33, 0.30, 0,30 (fourth/last trial). Results inconsistent with a decay explanation. Change the time for distractive task for all groups to 15s. Biointelligence Lab http://bi.snu.ac.kr

Relative Distinctiveness (2) Performance: 0.20, 0.28, 0.38. Release from PI “doesn’t work” (worth after change for one group) Baddeley (1976) offered an explanation that attributes this result to the relative, rather than absolute, duration of the distractor activity. Murdock (1960) proposed the model defines distinctiveness as the extent to which a stimulus stand out from other stimuli. Measure of how different each item is from all other items: where d – sum of all the interstimulus intervals + retention interval Result: As the retention interval increases, memory for the items at the end of the list gets worse and for the items in the beginning of the list gets better. Biointelligence Lab http://bi.snu.ac.kr

Discrimination problem Suggests that forgetting, in the sense of permanent loss, does not occur; there is only a failure to perform because of a difference in the stimulus conditions prevailing at encoding and at test. Eich and Brinbaum (1982) conducted a test, which showed that in “right conditions” with right retrieval cue subjects were able to recall many of the items that they previously could not. Biointelligence Lab http://bi.snu.ac.kr

Conclusions Each view, permanent loss and temporary laps, has its proponents and detractors. The permanent loss view suggests the information is gone forever, whereas the temporary laps view suggests that under different conditions with different ways of testing, the information might still be revealed. BUT, current theories of forgetting (supporting with tests) view memory as discrimination problem in which items will be recalled well if they are distinctive or stand out from competing items at the time of retrival. Biointelligence Lab http://bi.snu.ac.kr

Thank you. Biointelligence Lab http://bi.snu.ac.kr