Review #3 - Lecture#6 Tuesday Signal Detection Theory o...

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Lecture #6 Tuesday, January 22, 2008 Signal Detection Theory o Explains what happens when trying to detect something against background noise o Signal—what you are trying to detect o Noise—environment or background noise o Sensitivity—how well a person’s system can discriminate signal from noise Can be influenced by perceptual system and/or environment o Bias—tendency to say yes or no o Hit—correct yes; miss—incorrect yes; correct rejection—correct no; false alarm—incorrect no o Payoff effects—paying people more for a certain type of response Produces bias o Real world applications Diagnosis—you want someone with a high sensitivity Can produce bias by telling someone to focus on a certain area Context—the circumstances in which you see something o Subjective contours—not actually present, but you see because of context o Ambiguous letters—same exact letter read as 2 different letters based on context (the cat) o Objects out of context—difficult to recognize; implies top-down processing Higher levels influencing lower ones—words influence letters, letters influence features, etc. o Word Superiority effect—people recognize letters faster when they are in the context of a word than by themselves Guessing problem in old studies—alternative explanation for increased accuracy in the case of words Subjects were using first 3 letters to give themselves a 1/5 chance instead of 1/26 Solved by Reicher: word was presented on screen followed by mask (XXXX) and then presented with a choice of letters, all of which could form a word, thereby eliminating the possibility of guessing. Results: single letters and random letter strings produce the same
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This note was uploaded on 05/02/2008 for the course PSYCH 240 taught by Professor Gehring during the Winter '08 term at University of Michigan.

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Review #3 - Lecture#6 Tuesday Signal Detection Theory o...

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