The impact of a cognitive defusion intervention on behavioral and psychological flexibility: An experimental evaluation in a spider fearful non-clinical sample

• Defusion resulted in reduced spider phobic thought believability.
• Defusion produced increased flexibility in relational responding to aversive stimuli.
• Defusion may affect behavior in a theoretically consistent manner.

Acceptance and Commitment Therapy (ACT) utilizes cognitive defusion strategies to alter the function of unwanted, distressing thoughts so as to reduce their impact and foster greater psychological flexibility. Though defusion is linked to several positive outcomes (e.g., reduced thought believability, improved pain tolerance), it remains unclear whether such effects are associated with the behavioral process of defusion itself; namely, behavior that is relatively broad and flexible compared with behavior that is narrow and inflexible. To address this issue, the present study assessed the impact of a defusion intervention on behavior, as measured by the Implicit Relational Assessment Procedure (IRAP). Undergraduates high in spider fear (N=65) were randomly assigned to one of two interventions targeting phobic thoughts of spiders: a defusion intervention or a thought distraction intervention. A control condition (reading an article) was used to evaluate the relative impact of both interventions. Participants completed the IRAP and rating scales of believability and distress of target thoughts pre- and post-intervention. Consistent with expectation, defusion produced significantly greater pre- to post-intervention reductions in IRAP effects and thought believability relative to comparison conditions. The practical and scientific implications of the present findings, suggesting that defused behavior is broad and flexible relative to narrow and inflexible, are discussed.