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This study examined effects of experimentally-induced optimism on physical activity and stress reactivity with community volunteers. Using an intervention to induce short-term optimism, we conducted two harmonized randomized experiments, performed simultaneously at separate academic institutions. All participants were randomized to either the induced optimism intervention or to a neutral control activity using essay-writing tasks. Physical activity tasks (Study 1) and stress-related physiologic responses (Study 2) were assessed during lab visits. Essays were coded for intensity of optimism. A total of 324 participants (207 women, 117 men) completed Study 1, and 118 participants (67 women, 47 men, 4 other) completed Study 2. In both studies, the optimism intervention led to greater increases in short-term optimism and positive affect relative to the control group. Although the intervention had limited effects on physical activity and stress reactivity, more optimistic language in the essays predicted increased physical activity and decreased stress reactivity.


This is an Accepted Manuscript version of an article accepted for publication in The Journal of Positive Psychology, volume 18, issue 4, in 2023. It is deposited under the terms of the Creative Commons Attribution-NonCommercial License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited.


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Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License



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