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Homework Help: What's delta doing here?

  1. Nov 11, 2014 #1
    I last studied maths in school 10 years ago and we never used any Greek letters.

    1. The problem statement, all variables and given/known data

    Talking about contingency in classical conditioning in psychology. The sum is a calculation that people and animals seem to do in their heads to work out the probability that two stimuli will occur together based on how they've occurred together in the past. Or anyway it seems that they are aware of the results of this equation based on how they act.

    Here's my best attempt at a translation of what the Spanish textbook says:

    Positive contingency: if the occurrence of the Conditioned Stimulus (CS) is a good predictor of the occurrence of the Unconditioned Stimulus (US) (the light predicts well that the shock is coming) , the US has a higher probability of occurring when the CS has been previously prevented than when it hasn't. In this case there is excitatory conditioning.

    a = number of times US and CS were together
    b = number of times there was CS but no US
    c = " " "" "" there was US but no CS
    d = " " "" "" there was neither

    2. Relevant equations

    ΔP = P(EI|EC) – P(EI|noEC)= P1-P0= [a/a+b] –[c/c+d]

    P(US|CS > P (US|noCS)
    that is, P1>P0

    If the US only occurs in the presence of the CS and never without it, the contingency is perfect

    ΔP = P(US|CS) – P(US|noES) = 1-0 = 1

    3. The attempt at a solution

    Not looking for the solution.

    I understand the words, and I know that the equation represents the same thing.. but you might as well show me a picture of a squirrel and tell me she represents Crime and Punishment.

    If you can tell me what the Λ means in this case I'll be a bit closer to understanding I think.

    Any help you can give at all is appreciated. Thanks
  2. jcsd
  3. Nov 11, 2014 #2


    User Avatar

    Staff: Mentor

    The symbol Δ most often represents "change" or "difference." Here, ΔP is the difference in the two probabilities.
  4. Nov 11, 2014 #3
    Thank you!
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