Niemelá, P. Electrodermal responses as a function of quantified threat.Scand. J. Psychol., 1969,10, 19–56.—Threat was quantified by means of a 20 sec anticipation condition where the subject knew the exact time for the expected shock in advance, as well as the exact probability of receiving a shock. The probabilities used where 0.00, 0.25, 0.50, 0.75 and 1.00. The electrodermal responses (the amplitude of the skin resistance response, the amplitude of the skin potential response, and the number of electrodermal responses) during the anticipation period were found to vary systematically as functions of the probability of shock, and as functions of the time elapsed from the beginning of the experi