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Sunday, January 23, 2011

How knowledge leads to errors

How knowledge leads to errors
Our previous knowledge is a very valuable asset, but it can also lead to errors. Owens, Bower and Black (1979) illustrated this point well. They gave their university student participants a description of the activities performed by a character. For example, one of the sketches was about a student named Nancy. Here is the first part of that sketch: Nancy went to the doctor. She arrived at the office and checked in with the receptionist. She went to see the nurse who went through the usual procedures. Then Nancy stepped on the scale and the nurse recorded her weight. The doctor entered the room and examined the results. He smiled at Nancy and said, ‘Well, it seems my expectations have been confirmed.’ When the examination was finished, Nancy left the office. (p. 186) Half of the participants were told in advance that Nancy was worried that she was pregnant. These participants included between two and four times as many pieces of incorrect information when tested on their recall of the sketch. For example, some f them recalled ‘usual procedures’ as ‘pregnancy tests’. The errors were made in both recognition and recall tests. People have many expectations about how conventional activities (going to the doctor, a lecture, a restaurant) will proceed, and these provide schemas or scripts that can both aid and mislead. Bower, Black and Turner (1979), for example, studied the influence of such scripts on subsequent recall. In another part of their study, they also gave their participants stories based on normal expectations, but including variations from the norm. So, for example, a story about eating in a restaurant might refer to paying the bill at the beginning. When recalling these stories, participants tended to reorder them back to their schematic form or script. Other common errors involved including actions that would normally be expected in that context, but which had not been mentioned in the original story, such as looking at the menu. In general, the findings of these and similar studies indicate that people end to remember what is consistent with their schemas or scripts and to filter out what is inconsistent.

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