The purpose of this dissertation was to explore the relevance of autonomy, competence, and relatedness, the three innate psychological needs proposed by self-determination theory, to participant intrinsic motivation. The three needs of SDT have not previously been examined in an exploratory manner or applied to efficacy research in therapeutic recreation. If applied, therapists could use them to increase intrinsic motivation towards interventions in their participants.

The first manuscript discusses intrinsic motivation and self-determination and their presence in leisure and therapeutic recreation research. It details the experimental manipulation of autonomy, competence, and relatedness in a 2 x 2 x 2 design. A novel activity systematically varying in component support was introduced to 101 undergraduate students. The Intrinsic Motivation Inventory and Rated Needs Satisfaction were administered following the manipulation and participants were observed during a free-choice period to see if they chose to continue the activity as measures of intrinsic interest. Supporting competence and relatedness had main effects on intrinsic motivation. Supporting autonomy and relatedness together was also found to have a significant effect on intrinsic motivation. Implications for therapeutic recreation are discussed. The second manuscript reviews the importance of autonomy, competence, and relatedness in the lives of older adults, their impact on psychological well-being, and frequent absence in long term care settings. Research that addresses these deficits is then discussed with suggestions for application.