An investigation into the origins and functions of sexual dimorphism in human faces

The Perspective Hypothesis: if it is true that the characteristics of human facial dimorphism are directly linked to, and thus indicators of, height dimorphism; then changes in facial dimorphism will affect perceptions of stature height differences. If it is also true that head pitching behaviours manipulate observers’ perceptions of facial dimorphism; then by extension, the apparent height of the person pitching their head will also be manipulated. If it is also true that facial dimorphism and height dimorphism both impact perceptions of physical attractiveness and dominance characteristics; then this means that an individual pitching their head up or down in a certain fashion will change the perception of others regarding how dimorphic their face looks, how tall they are, how attractive they are, and how dominant they are – ultimately leading to mate selection outcomes. This hypothesis is tested across the studies; the first uses dynamic stimuli that pitch the head up or down in real time; the second uses geometric morphometric techniques; and the third uses an immersive virtual reality environment technique. The first and second studies are largely inconclusive, while the third study found some support for the hypothesis. The third study found that head pitching behaviour does impact perceptions of stature height, dimorphism, attractiveness, and dominance; but all in disparate ways that show no consistent overall pattern to suggest a common selection pressure.