Comparison of Probe Procedures in the Assessment of Chained Tasks

This translational study used an adapted alternating treatments design to compare the effects of single-opportunity probe (SOP) procedures, multiple-opportunity probe (MOP) procedures, and a preliminary fixed-opportunity probe (FOP) procedure on the acquisition of chained nonsense tasks for 12 college students. Nonsense tasks were carefully created to ensure equal difficulty across probes as well as to control for participants’ history with tasks. Following exposure to the probe procedures for 6 sessions, ascending trends were evident in the data in MOP conditions, zero-celerating in SOP conditions, and variations in responding in FOP conditions. The data suggest that both MOP and SOP procedures may result in testing threats to internal validity. The authors recommend that experimenters potentially abandon these procedures for alternative choices or use more than 1 procedure to represent the participant’s baseline performance. If MOP procedures are used, it is suggested that a minimum of 5 data collection opportunities occur prior to intervention. If SOP procedures are used, it is recommended that conclusions about the potency of the intervention be interpreted conservatively.