 Sober’s definition of adaptation is not constrained only to apply to organs or other traits that exhibit apparent design. Rather, clutch size (in birds), schooling (in fish), leaf arrangement, foraging strategies and all manner of traits can be adaptations (cf. Seger and Stubblefield 1996). Buller argues the more general point that phenotypic plasticity of various types can be an adaptation, because it arises in various organisms as a result of natural  selection.[9]  The difference here between Buller (and other philosophers and biologists) and evolutionary psychologists is a difference in the explanatory scope that they attribute to natural selection. For evolutionary psychologists, the hallmark of natural selection is a well functioning organ and for their critics, the results of natural selection can be seen in an enormous range of traits ranging from the specific apparent design features of organs to the most general response profiles in behavior. According to Buller, this latter approach opens up the range of possible evolutionary hypotheses that can account for human behavior. Rather than being restricted to accounting for our behavior in terms of the joint output of many specific modular mechanisms, we can account for our behavior by appealing to selection acting upon many different levels of traits. This difference in emphasis on what is important in evolutionary theory also is at the center of debates between evolutionary psychologists and behavioral ecologists, who argue that behaviors, rather than just the mechanisms that underlie them, can be adaptations (cf. Downes 2001). Further, this difference in emphasis is what leads to the wide range of alternate evolutionary hypotheses that Sterelny (Sterelny 2003) presents to explain human behavior. Given that philosophers like Buller and Sterelny are adaptationists, they are not critical of evolutionary psychologists’ adaptationism. Rather, they are critical of the narrow explanatory scope of the type of adaptationism evolutionary psychologists adopt (cf. Downes 2015).