Tripartite efficacy refers to the beliefs of the individuals within a dyad regarding personal abilities (self-efficacy), the partner's abilities (other-efficacy), or relation-inferred self-efficacy. This efficacy model has recently gained popularity in sports research (Jackson, Whipp, & Beauchamp, 2013), although there has not been any longitudinal research on efficacy beliefs and performance within this complex intra-dyad tripartite efficacy model. In a case study, we examined six individual players on a high school basketball team to explore any longitudinal changes in these tripartite efficacy beliefs through a season of play. On seven data collection periods, players completed the Basketball-Tripartite Efficacy Measure, and their game performance statistics were analyzed with an objective basketball individual performance formula. We found similar variations between participants' other-efficacy beliefs and the dyad partner's basketball performance score as well as between self-efficacy and individual performance score. Observational data from this case study lend some support to spiraling of self-efficacy and performance from repeated successes or failures and to perceived efficacy-performance plateaus that have been previously demonstrated in controlled experimental research. Importantly, this study suggests the presence of other-efficacy beliefs in their relationship to other-performance and to spiraling relationships between other-efficacy beliefs and other-performance, which have not been demonstrated previously.
