Peer pressure, community standards, and how much back bone the individual in question has to say, "no".
Persuasion and conformity are two or the three mains form of social influences (the other one is obedience).
Conformity is a change of behaviour that happens because of a real (or even imagined) group pressure. We normally use this term to indicate agreement with the majority, which can happen due to a desire to be liked or accepted, but also to be correct or to identify ourselves with a group of people or to be rewarded.
A lot of research has been carried to find out exactly what are the factors that push people to conform. They all agree that conformity is a pretty common human tendency, and people would rather conform than stand alone with their own opinions. Along with the already cited reasons, other factors that play a great role in conformity are:
- Group size: larger groups add to conformity pressures.
- Status: class influences conformity. We're more likely to agree with higher status' people rather than with marginalized or low status' ones.
- Public response: when people need to state their opinion or ideas in public, it's more likely that they will conform to society's norms
- Personality: if you're insecure and lack of self esteem, you'll probably be more likely to conform in order to feel reassured.
- In 1935, Sherif conducted an experiment that showed that in situations of ambiguity and uncertainty, people will always look up to find out what the group norm is, and they'll generally stick to it.
- Conformity can also on cultural differences. Generally Western countries see themselves as independent and self sufficient and are less likely to conform, whereas Eastern cultures are more rooted in family and community so they see the group's opinion as being more important than their own, thus they are more likely to conform.
If you want to know more about conformity, this webpage has loads of great information and examples all backed up with references. It is worth checking it out!
Persuasion is the use of social influence to make other people's change their mind or behaviours. It is a technique often used in business and advertising, to make you change your mind about a certain product or even news, but they can also be used unintentionally by your peers and friends.
Persuasion is more effective if you take into considerations these factors:
- authority: if we think that the person who's talking to us is an expert, or is "above" us, then we are more likely to be persuaded because we think that what he/she is saying is "official".
- likeability: If this person is a trusted friend, a lover, or a person we are attracted to, we are more likely to be persuaded.
- reciprocity: if we feel we owe this person something
- consistency: if we believe that what we're being persuaded of is consistent with our beliefs or commitments
- consensus: if we're being persuaded to do, buy, or say something that resonates with the public's opinion or trend, we'll be more likely to give in (goes hand in hand with conformity)
- scarcity: make you see the otherwise "missed opportunity" and make things more appealing simply because they're temporary or limited.
It is important to consider all these features and types of social pressures as being deeply connected to each other. Conformity is deeply linked to persuasion which can then result in obedience.
Hope this helps.