“…Although early work dates back to Tukey (1949), it is only recently that the problem of testing for additivity has been of real interest. We refer to Barry (1993), Eubank et al (1995), Gozalo and Linton (2001), Dette and Derbort (2001), Dette and Wilkau (2001), Derbort et al (2002), Sperlich et al (2002), Li et al (2003), De Canditiis and Sapatinas (2004) and Dette et al (2005) for various approaches to testing for additivity in the nonparametric regression models. Despite a growing number of works, almost none of them investigated the optimality of the proposed additivity tests.…”