We may be regularly told that you can't judge a book by its cover, but new research has thrown a spanner in the works.

Scientists now say that, when it comes to men, aggression or passivity is written all over the face.

Previous research revealed that men with broad, chubby faces tended to be more aggressive, and this latest study found that most people are able to spot an angry chap after just a quick split second glance.

Researchers showed 47 volunteers images of different men for a split second. They were then asked to rate how aggressive they seemed on a scale of one to seven.

And the participants were able to closely match both the men's aggression levels and the 'width to height ratio' (how broad the face is).

The Canadian scientists believe that these angry broad faces could be linked to testosterone, which influences adolescent growth and makes for a rounder face.

Published in the journal Psychological Science, the journal concluded: "This indicates differences in face shape may affect personality judgements, which may guide how we respond to individuals."

So if you're an angry man with a wide face, be warned... we can see you coming.