An alternate scoring method for the multiple stimulus without replacement preference assessment

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DeLeon and Iwata (1996) described the difficulties in applying the percentage approached scoring method to the multiple stimulus without replacement (MSWO) preference assessment relative to its application in the paired stimulus assessment. This scoring method may result in highly preferred items being misidentified as moderate or low preference. In the present study, the results of 57 MSWO assessments were scored using both the percentage approach method and a point weighting method. More items were identified as highly preferred with the point weighting method. Reinforcer assessments were conducted on a subset of stimuli judged to be high preference using the point weighting method but moderately or non-preferred when scored with the percentage approached method; all stimuli functioned as reinforcers. Copyright # 2005 John Wiley & Sons, Ltd. In the MSWO procedure (DeLeon and Iwata, 1996), a participant approaches a stimulus from a seven-item array. The item approached is not replaced in the array, resulting in items being presented in an unequal number of trials. DeLeon and Iwata evaluated potential reinforcers with a percentage approached scoring method similar to the one used in the paired stimulus preference assessment (Fisher et al., 1992), but noted that the percentage approached method may make it difficult to identify stimuli that could function as reinforcers. This scoring limitation is a result of the unequal number of opportunities to select each stimulus within and across MSWO sessions. The application of the percentage approach scoring methodology to the MSWO does not take this factor into account. In other words, the percentage approach scoring methodology as applied to the MSWO may result in false negatives, solely as a result of the scoring system. The purpose of the current study was to develop an alternate