Some invariances of the isosensitivity function and their implications for the utility function of money.

Four experiments were performed in which human observers reported whether or not they could detect the difference in amplitude between a pair of acoustic stimuli presented on each of several thousands of trials. In one experiment the probability that the pair differed was systematically varied. In another experiment the relative monetary value to the observer of reporting the differences was systematically varied. In a third experiment the instructions to the subject were systematically varied, and in a fourth experiment the monetary value of reporting a difference was altered by multiplying the rewards by a positive constant. In the first three experiments the iso-sensitivity function, the function that describes the relation between correct reports of a difference and false reports of a difference, was unchanged under all conditions. In the fourth experiment the absolute response probabilities of correct detections and false reports were reproduced even though five-fold changes in monetary value were made. This last result lends additional empirical support to the accumulating evidence that the utility function of money is a power function. (Author)