On the Choice of Parameters for the Lognormal Model for Response Times: Commentary on Becker et al. (2013)

In a recently published article in this journal, Becker et al. claim that, because of a missing slope parameter, the lognormal model for response times on test items almost never holds in practice. However, the authors' critique rests on a misrepresentation of the model, which already does have the equivalent of a slope parameter. More importantly, their extra parameter spoils the interpretation of the parameters for the test-takers' speed and labor intensity of the items necessary for a response-time model to be empirically meaningful while their proposed interpretation of the extra parameter seems unwarranted. An analysis of the authors' earlier empirical comparison between the original and their alternative version of the model does not seem to support much of a conclusion about the relative fit of the two models. Also, their simulation study conducted to demonstrate the necessity of the extra slope parameter appears to be based on data simulated in favor of their parameter.