070212 Chapter 3

070212 Chapter 3 - 2/12/07, Ch. 3 class notes A....

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2/12/07, Ch. 3 class notes A. CER--conditioned emotional reaction (also called conditioned suppression) An aversive (aversive US) CC procedure is superimposed on a hig ratoe of operant behavior so that suppression can be seen; not pssible in typical CC where the baseline of CR is 0; procedure developed by Estes & Skinner, 1941, who called conditioned suppression a ”conditioned emotional response” (CER). 1. Example: long-delayed conditioning; CS occurs long before US (e.g., 3 min) and overlaps US onset. 2. first you must establish a response that occurs at a high and stable rate, so that you will ultimately be able to see a decrease in rate—i.e., conditioned suppression (inhibition ) of responding from the higher level; usually use operant R of licking for water or lever-pressing for food pellets at a high rate. 3. then you superimpose an aversive classical conditioning procedure (e.g., CS tone preceding US shock —now that’s aversive!) on top of pre-established high rate of responding, so that when animal finally learns that onset of CS (e.g., tone) predicts that the US (shock) will be forthcoming, the ongoing operant responding will be disrupted in anticipation of shock as rat anticipates and prepares to receive shock, e.g., by freezing. The CER (conditioned suppression occurs because the response to the predictive CS is antithetical to or competes with the high rate of responding for, e.g., food pellets. Once shock (the US) has been delivered, however, t he animal resumes pressing at a high rate, as before, because it has learned that the CS (tone) perfectly (100%) predicts shock so that t here will be no shock until the CS occurs again. 4. suppression ratio —the suppression ratio expresses the degree of learning or conditioned responding the animal has exhibited on each CS-US trial. (See pp. 64-65—understand Fig. 3,2 on p. 65). a. In order to assess the degree of suppression during the CS (in the ISI), you must know how much the animal was responding immediately before the CS during a comparable period of time. So if the CS-US interval (ISI) is 3 min, then you must see how much rat responded during 3 min immediately before the CS (call that period “a” ) in order to determine the degree to which it then suppressed responding during the 3-min CS (call that period “b”). Because different animals respond at different rates, and the same animal may even respond differently during a given session, you must determine an individual animal’s responses in the period before each CS . b. The degree of suppression is the proportion of total responding that the rat exhibited during the CS. To calculate this, you determine the total amount of responding during the 3-min CS (b) and express it as a fraction of the total amount of responding in the 3 min before the CS plus during the 3-min CS. The more the rat has learned that the CS predicts the US is coming, the less it will respond during the 3-min CS relative to what it had responded before, but its reduction in responding during the CS is
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070212 Chapter 3 - 2/12/07, Ch. 3 class notes A....

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