Psychomorphospace—from biology to perception, and back: towards an integrated quantification of facial form variation

Several disciplines share an interest in the evolutionary selection pressures that shaped human physical functioning and appearance, psyche, and behavior. The methodologies invoked from the disciplines studying these domains are often based on different rhetorics, and hence may conflict. Progress in one field is thereby hampered from effective transfer to others. Topics at the intersection of anthropometry and psychometry, such as the impact of sexual selection on the hominin face, are a typical example. Since the underlying (evolutionary) theory explicitly places facial form in the middle of a causal chain as the mediating variable between biological causes and psychological effects, a particularly convenient conceptual and analytic scenario arises as follows. Modern morphometrics allows analysis of shape both “backwards” (by regressions on biology) and “forwards” (via predictions of psychology). The two computations are commensurate, hence the two kinds of effects can be compared and evaluated as directions in the same morphospace. We suggest translating the morphometric methodology of “Darwinian aesthetics” into this space, where psychological and other processes of interest can be coded commensurately. Such a translation permits researchers to relate the effects of biological processes on form to the perceptions of the same processes in one unified “psychomorphospace.”