An anonymous reader writes with news of research into the scientific literacy of college biology students. Earlier studies found that students tended to "rely on mainly informal reasoning derived from their personal experiences," so the researchers derived a new instructional framework that explicitly taught principle-based reasoning. While the number of students who used this method did increase, more than half continued to use informal reasoning, which the researchers say points to a flaw in the way biology is taught (PDF). "Most college-level instruction presents students with complicated narratives about the details of key processes (e.g., cellular respiration), but does not explicitly reinforce the use of key principles to connect those processes. Therefore, students are understandably occupied with memorizing details of processes without focusing on the principles that govern and connect the processes. ... As a result, students may leave an introductory biology course with the ability to recite the reactions in the Calvin cycle but still believing that plants obtain most of their mass from the soil rather than from the atmosphere, that plants photosynthesize but do not respire, or that the mass of a decomposing organism will primarily return to the soil."