Forget a glowing profile and an ever-expanding number of friends, Facebook users should ensure they post a complimentary photograph of themselves on the social networking site.
Researchers have found that a profile photo on Facebook tells viewers all they need to know to form an impression of someone and virtually no words are necessary.
In one experiment, college students who viewed a Facebook photo of a fellow student having fun with friends rated that person as extroverted - even if his profile said he was 'not a big people-person.'
Researchers have found that a profile photo on Facebook tells viewers all they need to know to form an impression of someone
The only exception is when a photo is out of the ordinary or shows someone in a negative light. In that case, people do use profile text to help interpret what kind of person is shown in the profile.
Lead author Brandon Van Der Heide, an assistant professor of communication at Ohio State University in the US, said: 'Photos seem to be the primary way we make impressions of people on social networking sites.
'People will accept a positive photo of you as showing how you really are. But if the photo is odd or negative in any way, people want to find out more before forming an impression.
In one study, 195 college students viewed a mock Facebook profile of a person who was supposedly a fellow student. The profile included a photo and a written 'about me' statement.
Participants were asked to rate how extroverted they thought the student in the profile was, on a scale of 1 (least extroverted) to 7 (most extroverted) based on the photo and text.
The participants viewed one of four profiles: in one, both the photo (a person shown enjoying a night out with friends) and the text ('I'm happiest hanging out with a big group of friends') suggested an extrovert.
A second profile had both a photo (a person alone on a park bench) and text ('I'm happiest curled up in my room with a good book') that suggested an introvert.
The other two profiles were mixed, with the photo suggesting an extrovert and the text an introvert, and vice versa.
Researchers said that on social networking sites users expect people to showcase themselves as happy, successful and sociable
The question the researchers wanted to answer was which mattered more - the photo or the text - in deciding whether the person was an extrovert or an introvert.
Results showed the photo was most important, Van Der Heide said.
When the extroverted photo was shown, it barely mattered whether the text suggested the person was an introvert or extrovert - most participants rated the person as an extravert.
But if the photograph suggested an introvert, people did pay attention to the text. If the text also suggested an introvert, participants rated the person as such. But if the text suggested the person was an extrovert, participants rated them as slightly less introverted.
Prof Van Der Heide said: 'They were still seen as introverted, because of their photo showing them alone on the park bench. But they got a little bump up in their extroversion rating because of their profile text suggesting they were extroverted.'
These results support a theory that people generally pay closer attention to information that could be viewed as negative or not normal, he said.
Researchers said that on social networking sites such as Facebook, users expect people to showcase themselves as happy, successful and sociable.
Prof Van Der Heide said: 'If the photograph fits that image, people have little reason to question his or her judgments about this person's characteristics,' he said.
'But if the photo shows something we didn't expect - someone who is more introverted, for example - viewers want to read the text and do a little more interpretation.'
He said the results were of interest because when people use text or photos alone to build an impression of someone, text may sometimes have a greater influence. This is especially true when conveying negative information.
In a separate study, 84 college students looked at one of the photos or read one of the text profiles used in the other experiment. But they had to rely simply on that text or that photo to rate the person's extroversion.
Results showed that the participants who read the introverted descriptions rated the person as significantly more introverted than did those who saw the introverted photos - suggesting text was most influential. However, there was no significant difference between how participants rated the person described as extroverted and the person whose photo suggested extroversion.
Prof Van Der Heide said: 'There are some cases where text may be more influential than photographs, particularly when they convey negative or unexpected information.'
He believes the results apply beyond Facebook to dating websites and other social networking sites. It should also apply to other traits beyond extroversion and introversion, such as social desirability and even political orientation. It all depends on what is shown in the photographs, and what clues viewers can glean from them.
The key is that people have certain expectations of the photos they view on social networking websites, he said.
He added: 'If your profile photo fits what they expect, observers may be unlikely to look very closely at the rest of your profile - they have already decided how they feel about you.
'But if your photo is not quite normal - either positively or negatively - people are going to pay a lot more attention to what you wrote.'
The findings appear in the Journal of Communication.