The Implicit Relational Assessment Procedure (IRAP) is increasingly used in applied and clinical settings, and yet many of the procedural variables of the IRAP have not been subjected to a systematic analysis. One such variable is the type of rules that are employed when instructing the IRAP and the effect this might have on resultant performance and obtained from the procedure. In the current thesis, three experiments assess the impact of three different types of rules or instructions on the IRAP. The instructions employed varied in the degree to which they specified parts of the relational network being assessed by the IRAP. The findings from these three studies show that the type of rule that is presented to participants during an IRAP may have a dramatic effect on the strength and direction of the trial-type effects that are produced by the measure. Furthermore, the type of instructions employed appear to interact with the order in which the IRAP blocks are presented (history-consistent versus history-inconsistent). The findings arising from the current thesis indicate that the behavioural dynamics that occur when participants complete an IRAP require extensive and systematic experimental and conceptual analyses, and this work will have an important bearing on research seeking to investigate the predictive validity of the IRAP in applied and clinical settings.