Women tolerate an unattractive man up to a point, but beware if he misbehaves. Then they'll easily shun him. So say Jeremy Gibson and Jonathan Gore of the Eastern Kentucky University in the US, after finding that a woman's view of a man is influenced by how handsome and law-abiding he is. Their study in Springer's journal Gender Issues has significance for those using dating sites or doing jury duty.

Discovering how someone can make a positive first impression is an important field of study because of its role in forming relationships. It is often based on physical appearance and whether someone sticks to social norms or not. Such impressions are made in a flash, but are not always correct. In what is called the "halo effect," people warm up to others with positive characteristics, such as handsomeness. The "devil effect" or "negative halo effect" comes into play when people assume that others possess so-called "bad" characteristics, based on traits such as unattractiveness..

Gibson and Gore tested if and how levels of attractiveness and conforming to social norms combine to influence 170 college women's perceptions of men. Two male faces -- one attractive, the other not -- bearing similar features were paired in two written scenarios. In the one, the man committed a major social no-no, in the other not.

The researchers found that whether a man transgressed a social norm was a much greater put-off than whether he was unattractive. Normally women do not feel differently towards a homely man who toes the line. If that same ugly duckling, however, transgresses the boundaries of right or wrong, a magnified or "double" devil effect comes into play. He is then viewed in an extremely negative light, much more so than would have been the case if he were handsome.

"The unattractive male is tolerated up to a point; his unattractiveness is OK until he misbehaves," says Gibson.

The halo and devil effect often comes into play when people view others' profiles on online dating sites. Based on their results, Gibson and Gore believe that unattractive men who provide unusual or alarming information in their profiles may not receive a second glance from women. This will not be the case for an Adonis posting the same information, or unattractive ones who do not violate these norms. In the judicial system, unattractive defendants are also known to receive more severe penalties than more attractive ones, even if they committed the same crime.

"A man who stands trial has already shown himself to have violated social norms in one way or another. If he is also unattractive, the magnified devil effect may result in a larger fine or sentence, as it could influence how negatively jurors view him and, as a result, the degree to which they believe him guilty of the crime," explains Gore.