Galvanometers measure the skin's ability to conduct electricity. why would this be relevant when determining whether a person is being truthful?
if skin is conducting little electricity, it indicates that the person is cold, which would indicate deception.
if skin is conducting little electricity, it indicates that the person is warm, which would indicate a fight or flight response, showing that the person is likely lying.
the more skin is conducting electricity, the more water there is on the skin, and the water is coming from sweat which may indicate nervousness and therefore a lie.
the less skin is conducting electricity, the less water there is on the skin, and the lack of water would point to dehydration, likely indicating a lie.