We thank the Crosslake Learning Resource Center (CLRC) for the use of previously developed IPSAs and administration software. This paper was improved based on thoughtful feedback from anonymous reviewers and from biology education research colleagues at the University of Georgia, especially Peggy Brickman and Tessa Andrews. We are also grateful to Paula Lemons for her advice about qualitative aspects of this study. This work was supported in part by the National Science Foundation under Grant No. DUE 1043079.