However, another theory proposed Dobbins and his colleagues is that the cortex is actually just refining learning of a particular response, and not refining its information about the object itself.
"In other words, we become more rapid with repetition of a decision task because we rapidly recover our prior responses, which under most circumstances is an appropriate and efficient strategy," Dobbins said. "Thus oftentimes the real work in making a decision about an object happens on the first encounter; subsequent trials, however, can be more easily solved using a short-cut method of simply recovering the previous response."
"What's fascinating about neural priming is that it occurs even in people with amnesia, who can't even remember events or objects," Dobbins said. "They also show this increase in performance with repetition despite being unable to consciously remember the previous encounters," Dobbins said. "Such findings have been the basis for the belief that we have separate systems for certain types of memory that function independently."
To test for this alternative theory, the researchers first asked subjects to judge whether objects such as an acorn, a stroller, a bicycle pump or a shuttlecock were "bigger than a shoebox." By using some items over and over, and introducing new items, they could study how the brain was responding to familiar versus new items and how performance was improving as subjects became skilled at the decision.
After analyzing the cortical activity during this task, they switched the task -- asking subjects to now judge whether many of the same objects were "smaller than a shoebox." Finally, they then restored the original "bigger-than-a-shoebox" question.
Thus, in the experiment, most of the
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Contact: Dennis Meredith
dennis.meredith@duke.edu
919-681-8054
Duke University
8-Mar-2004