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Poligraph tests test resistance or conductance?

  1. Jan 2, 2013 #1
    1. The problem statement, all variables and given/known data
    Question: "What does a polygraph test measure; skin resistance or conductance?"

    To me this is two sides of the same coin and it seems it must be measuring both.

    2. Relevant equations

    3. The attempt at a solution
    I thought that the person is acting as a resistor so I wrote down resistance, but the answer is conductance. I could just memorise the answer but I would like to understand why.

    I'm a psychology student so please speak slowly and without assuming any basic knowledge.
  2. jcsd
  3. Jan 2, 2013 #2


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    Staff: Mentor

    You are correct, it is technically two sides of the same coin. Resistance and conductance are related as R = 1/G, where R is resistance (measured in units of Ohms) and G is conductance measured in units of Siemens, and 1 Siemen is 1/(1 Ohm).

    In fields outside of pure physics or electronics, there is sometimes a tendency to make the "correct" answer one that is learned by wrote from the textbook.
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