One of the mammalian groups absent from the Finlay et al. study iscetaceans (dolphins, whales, and porpoises). Inclusion of cetaceanswould be useful for assessing the generalizability of the authors'conclusions. Recent findings suggest dolphins may differ from thegeneral pattern observed by Finlay et al. I encourage Finlay and hercolleagues to include developmental neurobiological data oncetaceans, when available.