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Quiz 2NAME:____________________________________ ID#:_________________
1. List the assumptions of the signal detection theory. Which two processes do ß (beta) and d' (d prime) represent?
The response:
1) depends on the intensity of the signal and the amount of noise (distinguishing between them)
2) depends on the two parameters ß and d'
3) is based on sensory detection and then on the decision made (yes/no)
ß = response criterion (bias). Affects how people will make decisions. If you reward a dollar for every correct detection, people will say yes all the time. If you reward a dollar for a correct detection but also say that they will lose 2 $ for false alarms, people will be more careful with the responses.
d' = the difference between the signal and the signal + noise distributions; the ability to distinguish between noise and the signal.
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2. What are three important characteristics of iconic memory (i.e., how does it last, how much and which type of information does it retain)?
Iconic memory seems to last around 1/4 of a second.
Iconic memory retains the visual features of the stimulus
The amount of information that can be stored is much greater than the 4 or 5 items that can be reported. Partial reports have shown that 12 items can be "remembered" using iconic memory.
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3. Define and illustrate with an example top-down and bottom-up processes.
Top-down processes - Higher level process affects the lower-level process. Knowledge is used to guide the lower-level process (e.g., when a person is far away, you predict that is your friend by using your previous knowledge. But when the person gets closer to you, you realize that it wasn't your friend).
Bottom-up processes - Processing of information begins with the low-level process that is passed along to higher level processes (e.g., you use this process when you see something you have never seen before and you don't have a higher level representation for it).
4. What are the main results of the visual search paradigm? What do reaction times tell us on the type of processing of visual features?
In the feature search, one needs only to look for a simple physical characteristic of the stimulus in order to detect the target stimulus, and the reaction time is about the same when the number of distractors increases (parallel process).
In the conjunction search, one has to look for the combination of two features (color + shape). One needs to focus attention on each item individually, so the reaction time increases as the number of distractor increases (serial process).
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5. What is the word superiority effect? How can we explain this effect in terms of activation of different cognitive codes?
It is easier to identify a letter if it is present in a word then if it is just present without a word.
A node with the higher activation is considered as a target stimulus. If the letter is present in a word, it activates the word level as well as the letter level. Consequently, the overall activation of the presentation of a letter in a word is higher than the presentation of a letter by itself.
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**Extra credit question**
6. What is visual agnosia? Which visual pathway is impaired in these patients?
Visual agnosia is caused by brain damage to the visual association cortex. Consequently, the patient can still see, since there is no damage to the eye itself or to the primary visual cortex. However, the patient cannot name what s/he sees, or grasps its significance. The ventral pathway (WHAT) is impaired in these patients.
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