Tall, masculine men aged around 35 years old perceived to be most dominant

The research, published by the SAGE journal Perception, sheds light on why Hollywood directors might choose certain actors to play leading roles.

The study was carried out by Carlota Batres, Daniel Re, and Professor David Perrett of the Perception Lab at the University's School of Psychology & Neuroscience.

Carlota and her team used computer graphic manipulations to make subtle alterations to images of men's faces. Participants in the study were asked their opinions on the men, based on how tall, masculine and old they appeared to be.

When the researchers made 25 year old men look 8 cm taller, up to a decade older, or made their faces more masculine (by for example increasing the prominence of their eyebrows), the onlookers thought the men looked more dominant.

Maximum dominance was achieved by increasing perceived height and masculinity while maintaining a man's age at around 35 years.

Carlota Batres, who led the research, said, "Understanding what influences dominance perceptions is important since a dominant appearance in male faces is associated with a variety of social outcomes, ranging from high rank attainment of cadets in the military to high levels of sexual activity in teenage boys.

"Dominant people are also favored as leaders during times of intergroup conflict and are more successful leaders in the business world. Hence, understanding what it is that makes someone look dominant is important given its influence on a variety of social outcomes."

Professor David Perrett, Head of the Perception Lab at the University of St Andrews added, "Such perceptions may also follow reality: taller men being more formidable opponents and strength increasing with age until a man gets to his mid-thirties."

The researchers say the study also provides some insight into casting choices made by film directors, since male leading roles are often played by actors who fit the dominance description in the study. Channing Tatum (1.85 meters tall, 35 years old), for example, is often cast to play strong and dominant characters, from the interplanetary warrior Caine Wise in "Jupiter Ascending" to the experienced male dancer "Magic Mike."