Teachers may wish to use open-ended learning activities and tests, but they are burdensome to assess compared to forced-choice instruments. At the same time, forced-choice assessments suffer from issues of guessing (when used as tests) and may not encourage valuable behaviors of construction and generation of understanding (when used as learning activities). Previous work demonstrates that automated scoring of constructed responses such as summaries and essays using latent semantic analysis (LSA) can successfully predict human scoring. The goal for this study was to test whether LSA can be used to generate predictive indices when students are learning from social science texts that describe theories and provide evidence for them. The corpus consisted of written responses generated while reading textbook excerpts about a psychological theory. Automated scoring indices based in response length, lexical diversity of the response, the LSA match of the response to the original text, and LSA match to an idealized peer were all predictive of human scoring. In addition, student understanding (as measured by a posttest) was predicted uniquely by the LSA match to an idealized peer. [The paper was published in: "Proceedings of the 20th International Conference on Artificial Intelligence in Education," p.133-143). Cham, Switzerland: Springer.]