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Unformatted text preview: 2/8/07, Ch. 3 class notes A. When (how) to measure CR: 1. test trials with CS alone--can see development of conditioning over trials (omit US 2. in interval between CS and US B. DEFINE ISI (CS-US interval). 1. The onse t of the conditioned stimulus (CS) in relation to the onset ogf theunconditioned stimulus (US) is a critical determinant of CC. 2. 1/2 s (500 msec) is optimal for adults; longer ISIs required for young S s of all species. [Explain Krasnogorski's idea that infants couldnt be classically conditioned before 6 months of age because their cortex was not sufficiently mature. Early studies of classical eyeblink conditioning seemed to support his idea, but tit urns out that they used an ISI that was appropriate for adults but was inappropriate for young infants, who require longer ISIs than adults.] See the Ivkovich experiment in text. We (Little, Lipsitt, and RC, 1984) found that 10-, 20-, and 30-day-olds exhibit CC of the eyeblink response with a 1500-msec ISI; for 4-5-month-olds, a 700-900-msec ISI is effective, but a 500-msec ISI is not. C. FACTORS THAT AFFECT CONDITIONING 1. CS Novelty--condition faster if CS is novel (remember to form a taste aversion, the CS had to be novel; class example: my son Christopher and concentrated orange juice + nausea (formed taste aversion) vs. pizza + nausea (no taste aversion) 2. US/CS Intensity, Salience (salience is how attention-getting a stimulus is relative to the background level of stimulation); an discriminable change in stimulus intensity is salient, for example, whether the new stimulus level is higher or lower than the background level! Even the total cessation of noise from children stimulus level is higher or lower than the background level!...
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- Spring '06