With respect to the analogue functional analysis conducted in Experiment , the presentdata seemed undifferentiated for Mario, because high levels of stereotypy occurred during allconditions. One possible explanation is that his stereotypy served multiple functions and noneof stimulation provided in conditions could compete with his stereotypy successfully (Harding,Wacker, Berg, Barretto, & Ringdahl, 00 ). However, these patterns of stereotypic responsesoccurred might also suggest that none of the alternative activities available during all assessmentconditions could compete with the sensory reinforcers maintaining stereotypic behaviors, andthe functions of stereotypy might be merely under control of sensory reinforcement. That is,specific types of antecedents and consequences selected for the most of the assessments maynot be relevant to the actual maintaining factors in the environments. This explanation wassupported by Experiment which showed Mario's stereotypy was merely maintained by sensoryconsequence (finger stimulation). Such perspective was further supported by Iwata et al. ( )who have shown three subjects exhibited extremely high levels of self-injurious behaviors duringalmost all assessment conditions and suggested that these behaviors were maintained by sensoryreinforcement. More evidence came from Vollmer, Marcus, and LeBlanc ( ) who studiedthe stereotypic mouthing behaviors of three students with developmental disabilities and foundthat high levels of such behaviors occurred across all test conditions. Their results of study alsosuggested that sensory consequences contributed these aberrant behaviors.Another explanation regarding appearance of such undifferentiated assessment may bethat some unknown antecedent events influenced this aberrant behavior. For instance, someresearchers have shown that idiosyncratic antecedent factors can be relevant to the occurrenceof disruptive behavior during assessment conditions (Carr, Yarbrough, & Langdon, ). Intheir study, for one subject, the initial analysis did not reveal the high levels of aberrant behavioroccurred in attention and demand conditions. A subsequent descriptive analysis showed that lowlevels of such behavior occurred in these conditions often accompanied by holding small itemsin his hand. Further manipulation of presence or absence of small items during these conditionsshowed that such aberrant behavior occurred in higher levels during demand conditions whensmall items were deprived from the test condition.Moreover, specific sensory consequences were detected in our study and showed that fingerstimulation was one source to execute its impact on Mario's stereotypic behavior. This findingwas further supported by a prior study (Goh et al., ) which has shown that finger stimulation