The young men with a paternal history of AAB had lower intercepts and less change over time than the low-risk participants. It is possible that the reduced slope characterizing this trajectory may be an artifact of the participants at highest risk having P300 amplitude at the start of the study close to an absolute psycho-physiological lower limit. The reduced change over time may reflect a floor effect consistent with Wilder’s (1967) law of initial values. One way to examine this possibility is to assume that the amplitude of the response to the neutral nontarget stimuli represents this lower limit and to then determine to what degree the target amplitude approximates this value at the time of the earliest assessment. A mixed model with task condition (neutral or target) as a fixed factor, amplitude measures nested within participants, and participants nested within families was fit to the Time 1 P300 amplitude of the paternal AAB group using PROC MIXED. This analysis was restricted to only the 40 men with data from the first and last assessments. In this group target, amplitude
