I've noticed a general trend in my teaching whereby my Intro Ethics students generally do almost a full letter grade better on average than my regular Intro students (e.g. a B+ to the Intro's B-). I don't think it's because my Ethics class is easier, because the pattern extends to individual test questions concerning material that I include in both classes, such as the meaning of the word 'valid.'
Have others noted the same trend? Zero and his commenters consider some possible explanations. Is this the case, and if so, what does it tell us about how these seminal introductory courses should be approached?