1. A method of determining the probability of ruminating behavior in a person of known age, sex and use of medication, using an electroencephalographic machine operable for reading human brain waves, a computer operable for receiving the output of said electroencephalographic machine, a device operable to display a paradigm of a pre-selected design, illumination, and frequency, said computer also capable of synchronizing the recording and averaging said brain waves when the paradigm is illuminated, which comprises: attaching the electrodes of an electroencephalographic machine to the scalp of said person in accordance with the American Electroencephalographic Society's Electrode Placement International 10-20 Standard System for measuring a person's brain waves; positioning said person to view a paradigm to visually evoke a potential in said person's brain; displaying to said person a plurality of sequentially displayed paradigms and simultaneously measuring the brain waves of said person for each of the displayed paradigms during the time of display; averaging said brain waves to determine the visually evoked response to said displays of said paradigms; measuring the maximum amplitude, in microvolts, of said visually evoked response at a plurality of points in time over approximately 500 ms of time after termination of each of the displays of said paradigms; transmitting to said person a plurality of audio signals and simultaneously measuring the brain waves of said person for each of the audio signals during the time said auditory signals are being transmitted; averaging said brain waves to determine the auditory evoked response to said transmissions of said audio signals; measuring the maximum amplitude, in microvolts, of said auditory evoked response at a plurality of points in time over approximately 500 ms of time after termination of each of the transmissions of said audio signals; conducting and recording the quantitative electroencephalographic activity of said person; measuring the amplitude of said quantitative electroencephalographic activity; conducting a logistic regression analysis of said visually evoked response over a period of time of approximately 500 ms after termination of each of said displays of said paradigm, said auditory evoked response over a period of time of approximately 500 ms after termination of said transmission of said audio signals, said electroencephalographic activity, and said person's age, sex, and whether said person is taking medication, to establish a predictive algorithm; and computing the probability of ruminating behavior using said algorithm.