Document Type


Degree Name

Doctor of Philosophy (PhD)



Program Name/Specialization

Social Psychology


Faculty of Science

First Advisor

Dr. Nancy Kocovski

Advisor Role

Doctoral Supervisor


Mindfulness has been shown to lead to reductions in psychological distress and improved well-being, but there is limited research on the mechanism of change. A cognitive shift in perspective has been suggested as a possible mechanism of change. Three different terms appear to refer to this shift in perspective: 1.Decentering, developed from cognitive behavioural therapy, involves the ability to observe one's thoughts and feelings as solely being events of the mind. 2. Defusion, developed from acceptance and commitment therapy, focuses on the ability to separate or distance from one’s thoughts, and 3. Metacognitive awareness, developed frommindfulness-based cognitive therapy, involves experiencing negative thoughts as mental events rather than as fact. This dissertation empirically examines this cognitive shift in perspective over three studies. In Study 1, we found a modest association between trait measures of decentering and fusion (the counter process to defusion) although neither was found to be associated with metacognitive awareness. There were some similarities with regards to the strength of correlations with variables such as depression and social anxiety, but differences also emerged with variables such as mindfulness and cognitive reappraisal, suggesting that perhaps the measurement tools are capturing constructs more differently than expected. In Study 2, we examined whether it was possible to induce state changes in decentering and defusion. To do this,an exercise from each of the aforementioned research traditions was selected. We found that the defusion and metacognitive awareness exercises led individuals to be less fused with their thoughts compared to the decentering exercise. There were no significant differences found on our decentering outcome measure. These findings suggested that being fused in thoughts may be easier for individuals to report. Finally, for Study 3 we experimentallymanipulated defusion after individuals received one of three audio interventions (mindfulness, relaxation, or control). Against what was expected, results suggest that when combined mindfulness + defusion led to more fusion and more post-event rumination for individuals with high social anxiety. Collectively, these three studies provide insight into three constructs that are used interchangeably in the literature. Study 3 also helps to contribute to our understanding about whether cognitive defusion is one of the mechanisms through which mindfulness is leading to favourable outcomes.

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