Better at What?

In reading the title of Johnson et al.'s (2010) article on synthetic validity, I immediately asked myself “Better at what?” Motor oil serves three functions in internal combustion engines: lubricate, cool, and clean engine parts. There is little doubt that synthetic motor oil does all three of these better than nonsynthetic motor oil, although some might argue that it is not as cost effective. Johnson et al. described two approaches to synthetic validity and then argued why synthetic validity is “the best approach for many situations.” I strongly agree with their contention that synthetic validity is “practically useful” and with their less directly stated contention that it also holds value in developing theory. Hence, I will limit my comments exactly to how synthetic validity inferences might best contribute to the complimentary goals of advancing theory and practice, although these might cause Johnson et al. to rethink some of their observations.