Several studies have examined the impact that teammates have on one another. For example, Gould and Kaplan (2008) look at knowledge-sharing that takes place among teammates. Specifically, they consider the peer effect of the baseball player Jose Canseco, a self-professed steroid-user, and whether workers (baseball players) learn productive skills from their co-workers (teammates) even if those skills are unethical (in this case, the use of steroids). According to Canseco’s autobiography, he increased the productivity of his teammates by introducing them to steroids. Gould and Kaplan test his claim by examining the performance of his teammates before and after the time that they played with Canseco. They find the effect on his teammates was consistent with Canseco’s claims, making a case for the presence of knowledge-sharing among teammates.