The current thesis investigated the methodological and clinical implications of rulefollowing behaviour. The research program comprised eight experimental studies, including the match-to-sample methodology and the use of radiant heat apparatus. Chapter 1 provides a review of the available literature on rule-following, including empirical evidence of its clinical implications. Chapter 2 incorporated four studies that examined rule-following vs. contingency adaptation in a simple automated match-to-sample task based on previous research (McAuliffe, 2004). In Experiment 1 (n=16), three Pliance conditions (with differing levels of Experimenter involvement) were compared to a Tracking condition. In simple terms, the two types of condition were distinguished in terms of the Experimenter’s knowledge of the experimental rules with which participants had been provided. Although the results demonstrated a clear distinction between pliance and tracking, the experimental control of either was not as expected. Specifically, participants in Pliance showed evidence of tracking, with strong adaptation to changing experimental contingencies. In contrast, participants in Tracking showed evidence of pliance, with perseverative rule-following even when the rules became inconsistent with the task contingencies. In the former conditions, the activities of the Experimenter appeared to have little influence over responding. Experiment 2 (n=24) incorporated minor modifications to experimental instructions based on participant feedback, as well as a greater sample size, to establish more reliable experimental control over pliance and tracking. The results showed evidence of pliance in both Tracking and Pliance conditions, thus raising further issues about experimental control. To address these issues, Experiment 3 (n=16) replicated McAuliffe’s original procedure without modification, paying particular attention to the original instructions and with the removal of the instructions after participants had read them. The results recorded here provided the clearest distinction between pliance and tracking (participants in Tracking demonstrated tracking and Pliance demonstrated pliance), but were more like outcomes McAuliffe had reported with depressed, rather than non-depressed, participants. Experiment 4 (n=16) replicated Experiment 3, but participants retained the instructions after they had read them. This variable appeared to have had some influence over the previous outcomes when the data indicated a reduction in the distinction between pliance and tracking, with participants in Tracking showing increasing pliance and participants in Pliance showing increasing tracking. Chapter 3 incorporated two studies that compared pliance and tracking in the context of different rules (tolerance vs. subjectivity) for coping with experimentallyinduced pain. Experiment 5 (n=40) attempted to replicate previous research by Hayes and Wolf (1984), but replaced the cold pressor task with the radiant heat apparatus. Inconsistent with previous evidence, four of the five conditions recorded decreases in heat tolerance, with the exception of the Pliance/Subjectivity condition. Experiment 6 (n=40) replicated Experiment 5, but with the Experimenter absent during the heat tests. The results indicated a notable distinction between pliance and tracking, in which pliance was associated with tolerance increases and tracking was associated with tolerance decreases. Chapter 4 incorporated two studies that compared brief therapeutic acceptancebased interventions vs. rules to determine which would exert greater influence on heat tolerance. Experiment 7 (n=32) systematically compared acceptance-based vs. placebo based interventions and rules. Although the results were partly consistent with predictions when both Placebo conditions were associated with tolerance decreases, the outcomes for Acceptance were not as expected. Specifically, the Acceptance Intervention resulted in marginal tolerance decreases, while the Acceptance Rule produced only marginal tolerance increases. The final study, Experiment 8 (n=32), compared acceptance interventions and rules in pliance vs. tracking contexts to determine what impact this variable may have exerted on the previous findings. The results from Experiment 8 indicated that pliance was associated with greater tolerance increases than tracking and the intervention overall produced better tolerance than the rule. The current research raised a number of methodological and conceptual issues that contribute to the existing literature on rulefollowing behaviour and these are discussed in the final General Discussion Chapter 5.