A man's trustworthiness is judged by the color of his eyes and the shape of his face, a new study suggests.

Researchers from the Czech Republic found that people viewed brown-eyed faces as more trustworthy than faces with blue eyes, except if the blue eyes belonged to broad-faced man.

In the study, published in the journal PLOS ONE, researcher Karel Kleisner and colleagues from Charles University wanted to identify facial features that made a person look trustworthy.

Researchers asked participants in the study to rate male and female faces for trustworthiness based on two features: eye color and face shape.

The findings show that a significant number of participants perceived brown-eyed faces to be more trustworthy than blue-eyed faces, regardless of whether the faces were male or female.

Researchers found that rounder male faces with fuller mouth and larger chin were judged to be more trustworthy than narrow faces. However, researchers found that the shape of a female face did not really have an effect on how trustworthy it appeared to participants.

Researchers wanted to determine whether face shape or eye color was more important when assessing trustworthiness. So to test which of the two features was more important, they presented participants with photographs of faces that were identical in all ways except for eye color.

Surprisingly, the researchers found that both brown and blue eyes were judged as equally trustworthy.

They concluded that it isn't that brown eyes are perceived to be more trustworthy than blue eyes, but that the facial features associated with brown eyes that made a face more trustworthy.

"We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes," researchers wrote in the study.