Abstract
Rouder & Haaf (2021) provide a valuable recipe for testing whether there are qualitative differences. This should hasten the day when psychologists routine consider individual participant data, rather than just the average of the participants’ data. Work remains to be done, however, on how to approach the issue of individual differences with the small-N, many-trials tradition that dates back to the beginning of experimental psychology and continues today in some areas, particularly cognitive modelling and perception.