We acknowledge that there are many potential strategies for testing the degree to which a single trait can explain the covariation among all other traits, and recognize the possibility that different GFP estimation methods could lead to different conclusions about the consistency of the GFP across measures. Indeed many approaches have been employed to identify the GFP in previous research (Ferguson et al., 2011). Because standards for factor analytic practice are fuzzy (e.g., Hopwood & Donnellan, 2010; Marsh, Hau, & Wen, 2004) there exists a good deal of subjectivity in the interpretation of these kinds of results. In this context proponents of the GFP with considerable factor analytic expertise might find a way to indentify a very specific model or small number of models that would appear to support the GFP proposal. However, we suspect that such models would likely fail to generalize to new samples and may even contradict less controversial features of the personality trait hierarchy (e.g., which traits from the Big Five level load onto the Big Two).
