Everyone's got a story about how they thought a certain friend was mean the first time they met, but realised later that he or she is actually the nicest person ever.

Generally, you've only got a few seconds to make someone want to spend more time with you. Everything matters — from your last name to the smell of your sweat (gross, we know).

Below, Business Insider rounded up various scientific findings on the traits and behaviours that make people dislike you, both online and in person.

1. Sharing too many photos on Facebook

If you're the kind of person who shares snapshots of your honeymoon, cousin's graduation, and dog dressed in a Halloween costume all in the same day, you might want to stop.

A 2013 study found that posting too many photos on Facebook can hurt your real-life relationships.

"This is because people, other than very close friends and relatives, don't seem to relate well to those who constantly share photos of themselves," lead study author David Houghton, of Birmingham Business School, said in a release.

Specifically, friends don't like it when you've got too many photos of family, and relatives don't like it when you've got too many photos of friends.

Ben Marder, of the University of Edinburgh, also worked on the study, and warned: "Be cautious when sharing and think how it will be perceived by all the others who may see it. Although sharing is a great way to better relationships, it can also damage them."

2. Having too many, or too few, Facebook friends

In a 2008 study, Michigan State University researchers asked college students to look at fictional Facebook profiles and decide how much they liked the profiles' owners.

Results showed that the "sweet spot" for likability was about 300 friends. Likability ratings were lowest when a profile owner had only about 100 friends, and almost as low when they had more than 300 friends.

As for why 300-plus friends could be a turn-off, the study authors write, "Individuals with too many friends may appear to be focusing too much on Facebook, friending out of desperation rather than popularity."

On the other hand, the college students doing the evaluation each had about 300 Facebook friends themselves. So the researchers acknowledge that in a population where the most common number of Facebook friends is 1,000, the sweet spot for likability could be 1,000.

Keep in mind, though, that a 2014 survey found that the average number of Facebook friends among adult users was 338.

Interestingly, the study also suggested that participants weren't consciously aware that they liked people less when they had too many or too few Facebook friends.

3. Disclosing something extremely personal early on in a relationship

In general, people like each other more after they've traded confidences. Self-disclosure is one of the best ways to make friends as an adult.

But psychologists say that disclosing something too intimate — say, that your sister is having an extramarital affair — while you're still getting to know someone can make you seem insecure and decrease your likability.

The key is to get just the right amount of personal. As a 2013 study led by Susan Sprecher at Illinois State University suggests, simply sharing details about your hobbies and your favorite childhood memories can make you seem warmer and more likable.

(Flickr / Pedro Ribeiro Simões (Flickr / Pedro Ribeiro Simões)

4. Asking someone questions without talking about yourself at all

That same 2013 study by found an important caveat to the idea that self-disclosure predicts closeness: It has to be mutual. People generally like you less if you don't reciprocate when they disclose something intimate.

In the study, unacquainted participants either engaged in back-and-forth self-disclosure or took turns self-disclosing for 12 minutes each while the other listened. Results showed that participants in the back-and-forth group liked each other significantly more.

As the authors write, "Although shy or socially anxious people may ask questions of the other to detract attention from themselves, our research shows that this is not a good strategy for relationship initiation. Both participants in an interaction need to disclose to generate mutual closeness and liking."

5. Posting a close-up profile photo

If your LinkedIn profile features an image of your face practically smushed up against the camera, you'd be wise to change it.

Research from California Institute of Technology suggests that faces photographed from just 45 centimeters — about 1.5 feet — away are considered less trustworthy, attractive, and competent than faces photographed from 135 centimeters, about 4.5 feet, away.

(Carlos Pacheco/Flickr (Carlos Pacheco/Flickr)

6. Hiding your emotions

Research suggests that letting your real feelings come through is a better strategy for getting people to like you than bottling it all up.

In one 2016 study, University of Oregon researchers videotaped people watching two movie scenes: the fake-orgasm part of the movie "When Harry Met Sally" and a sad scene from "The Champ." In some cases, the actors were instructed to react naturally; in another they were instructed to suppress their emotions.

College students then watched the four versions of the videos. Researchers measured how much interest the students expressed in befriending the people in the videos, as well as their assessments of the personalities of the people in the videos.

Results showed that suppressors were judged less likable — as well as less extroverted and agreeable — than people who emoted naturally.

The researchers write: "People … do not pursue close relationships indiscriminately — they probably look for people who are likely to reciprocate their investments. So when perceivers detect that someone is hiding their emotions, they may interpret that as a disinterest in the things that emotional expression facilitates — closeness, social support, and interpersonal coordination."

(Carlos Pacheco/Flickr (Carlos Pacheco/Flickr)

7. Acting too nice

It makes logical sense that the nicer and more altruistic you seem, the more people will like you. But some science suggests otherwise.

In a 2010 study, researchers at Washington State University and the Desert Research Institute had college students play a computer game with four other players, who were really manipulations by the researchers.

Here's how one of the study authors explained the study procedure in The Harvard Business Review:

"Each participant was placed in a five-person group, but did not see its other members. Each was given endowments that they could in their turn choose to keep or return, in whole or in part. There was some incentive to maximize one’s holdings, but not an obvious one.

"(The participants were told that, at the end of the semester, a random drawing of their names would be held and those few who were chosen would have their holdings converted to Dining Services coupons redeemable at campus eateries.)"

Some of the fake participants would give up lots of points and only take a few vouchers — a rather altruistic behavior. As it turns out, most participants said they wouldn't want to work with their unselfish teammate again.

In a similar, follow-up experiment in the same study, some said the unselfish teammate made them look bad; others suspected they had ulterior motives.

8. Humblebragging

In an effort to impress friends and potential employers, some people disguise bragging as self-criticism. This behavior, otherwise known as "humblebragging," could be a turn-off, according to a recent study from Harvard Business School.

In the study, college students were asked to write down how they'd answer a question about their biggest weakness in a job interview. Results showed that more than three-quarters of participants humblebragged, usually about being a perfectionist or working too hard.

Yet independent research assistants said they'd be more likely to hire the participants who were honest, and found them significantly more likable. Those students said things like, "I'm not always the best at staying organized" and "Sometimes I overreact to situations."

Another alternative in a job-interview situation is to talk about weaknesses that don't directly relate to the position — for example, a fear of public speaking if you're applying for a writing position.

9. Getting too nervous

Never let 'em see — or smell — you sweat. Research suggests that the odor of your nervous sweat may subconsciously influence people's judgments of your personality.

In 2013, researchers at the Monell Chemical Senses Center had participants watch videos of women in everyday situations, like working in an office and taking care of a child. While watching the videos, they sniffed three kinds of sweat: sweat that someone had produced while exercising, sweat produced during a stressful situation, and sweat produced during a stressful situation that had been covered up with antiperspirant.

Participants were then asked to rate the women on how competent, confident, and trustworthy they seemed.

Results showed that participants rated the women lower on all measures when they smelled the stress-induced sweat. When they smelled the stress sweat that had been covered up with antiperspirant, they rated the women more positively.

10. Not smiling

(Flickr/stevendepolo (Flickr/stevendepolo)

When you're at a networking event and meeting lots of new people, it can be hard to keep a smile plastered on your face. Try anyway.

In a University of Wyoming study, nearly 100 undergraduate women looked at photos of another woman in one of four poses: smiling in an open body position, smiling in a closed body position, not smiling in an open body position, or not smiling in a closed body position. Results showed that the woman in the photo was liked most when she was smiling, regardless of her body position.

More recently, researchers at Stanford University and the University of Duisburg-Essen found that students who interacted with each other through avatars felt more positively about the interaction when the avatar displayed a bigger smile.

Bonus: Another study found that smiling when you first meet someone helps ensure that they'll remember you later.

11. Acting like you don't like someone

Psychologists have known for a while about a phenomenon called "reciprocity of liking": When we think someone likes us, we tend to like them as well.

In a 1959 study published In Human Relations, for example, participants were told that certain members of a group discussion would probably like them. (These group members were chosen randomly by the experimenter.) After the discussion, participants indicated that the people they liked best were the ones who supposedly liked them.

More recently, researchers at the University of Waterloo and the University of Manitoba found that when we expect people to accept us, we act warmer toward them — thereby increasing the chances that they really will like us. So even if you're not sure how a person you're interacting with feels about you, act like you like them and they'll probably like you back.

If, on the other hand, you don't express fondness for the person you're meeting, you could potentially turn them off.

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12. Having a hard-to-pronounce name

We know: This one's really not fair.

But here's the science: A 2012 study, by researchers at the University of Melbourne, the University of Leuven, and New York University, found that people with more complicated last names are judged more negatively.

In one experiment included in the study, undergraduate participants read a mock newspaper article about a man running for an upcoming local council election. Some participants read about a man with a relatively easy-to-pronounce last name (Lazaridis or Paradowska); others read about a man with a harder-to-pronounce name (Vougiouklakis and Leszczynska).

As it turns out, participants who'd read about the man with the simpler name said that candidate was a better fit for the government position than participants who'd read about the man with the more complicated name.

13. Name-dropping

It can be tempting to mention that famous author who graduated from your alma mater in order to impress your conversation partner. But the tactic can backfire.

That's according to researchers at the University of Zurich. In 2009, they published a paper suggesting that name-dropping makes people seem both less likable and less competent.

For the study, University of Zurich students interacted with "partners" via email (the emails had really been generated by the researchers).

In some emails, the partner mentioned that Roger Federer was his friend and that they'd worked out together. In other emails, the partner only mentioned that Federer was a friend. In another set of emails, the partner mentioned that he or she was a fan of Federer. And in some emails, the partner didn't mention Federer at all.

Results showed that the stronger the supposed association between the partner and Federer, the less participants liked their partner. The researchers found that was largely because participants felt their partners were manipulative.