“…The categorical perception hypothesis is in line with insights from evolutionary biology linking categorization to survival and the failure to categorize stimuli to negative emotional responses (Burleigh & Schoenherr, 2015). Psychological research has further demonstrated that category boundaries exist for identification of facial images along morphed spectra (Cheetham, Pavlovic, Jordan, Suter, & Jancke, 2013;Cheetham et al, 2011;Cheetham, Suter, & Jancke, 2014;Looser & Wheatley, 2010;Yamada, Kawabe, & Ihaya, 2013; see Figure 1 for an illustration of the category boundary concept), and that discrimination performance reaches its peak when agent images straddle the category boundary, indicating categorical ambiguity (Cheetham et al, 2011(Cheetham et al, , 2014Looser & Wheatley, 2010). Increased categorical ambiguity has been reported to coincide with negative stimulus evaluations in some studies (Burleigh, Schoenherr, & Lacroix, 2013;Ferrey, Burleigh, & Fenske, 2015;Yamada et al, 2013) but not in others (Cheetham et al, 2014;Looser & Wheatley, 2010;.…”