"Virtual Clinical Trials" simulations were designed to highlight neuroscience research and reinforce experimental design through the recreation of published clinical trials. This paper reports the effectiveness of "Virtual Clinical Trials" simulations in improving knowledge of concepts related to the experimental design process and attitudes toward clinical trials, science careers, and scientific possible selves among high school Anatomy and Physiology students. A three-arm experimental design (N=525) was implemented to test the "dose effect" of playing one verses two simulations. Results confirmed that all students increased their knowledge of experimental design concepts and improved their attitudes toward clinical trials, with students completing two simulations having the greatest shifts. All students also had a small, but significant improvement in scientific possible selves, though completion of two simulations did not confer any extra benefits. There were no detectable differences in clinical trial career interest. Additionally, the simulations were beneficial to students regardless of gender or ethnicity for knowledge gain and attitude change. With regard to measures of satisfaction and engagement, females expressed greater satisfaction with the simulations and minorities were more engaged. The results demonstrate that knowledge gain, attitude change, and the promotion of science identity are achievable through exposure to simulations, while shifts in career interest are not as consistently realized.