Adaptive psychophysical procedures have come into widespread use for the estimation of psychophysical performance. Their popularity arises from their speed of implementation and efficiency in the stimulus levels far removed from the selected target values are seldom presented. Thus, experimental time and subject energy can be devoted to a precise delineation of performance at and around the target or threshold region. However, sometimes it is valuable to be able to describe a subject's performance across a wide range of stimulus values by construction of a psychometric function showing how performance changes with changing stimulus values. Since adaptive tracking procedures are specifically assigned to avoid stimulus levels far from the target value, the psychometric function constructed from the data in the track may be precisely defined near the target where there are many trial presentations for each level, but be a poor reflection of performance at levels removed from the target. While some authors have attempted to analyze the trial-by-trial data produced by an adaptive track to construct a psychometric function, there is little evidence that the functions they report do, in fact, represent the underlying function governing subject performance. A series of computer simulations was undertaken to assess the validity and accuracy of psychometric functions generated from data collected in adaptive tracking procedures. (sdw)
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