Social Impact Theory Explained

Social impact theory was created by Bibb Latané in 1981, who is also credited as one of the psychologists who brought the bystander effect to light.

Latané’s theory suggests that we are greatly influenced by the actions of others. We can be persuaded, inhibited, threatened, and supported by others.

Latané’s theory proposes that individuals can be the sources or targets of social influence. Social impact theory is a model that conceives of influence from other people as being the result of social forces acting on the individual.

The likelihood that someone will respond to social influence is thought to increase with the strength of the source, the immediacy of the event, and the number of sources exerting the impact.

A division of impact means that the social impact gets spread out between all the people it is directed at. If all the influence is targeted at a single individual, this puts a huge pressure on them to conform or obey.

However, if the influence is directed at two people, the influence is halved.

The more targets there are, the more pressure is shared. This idea is known as diffusion of responsibility. This can explain how the bystander effect can occur in a situation where one person needs help, and a group of people can watch and not feel responsible for helping, compared to if they were the only other person present.

Social Impact Theory’s Three Variables

In Social Impact Theory, “i” is the impact. It’s a function of three variables: strength (s,) immediacy (i,) and the number of sources (n.) If any of these are significantly high or low, it will have a serious effect on the impact on the target.


This is how important influencing an individual or group of people is to the person. There are thought to be two categories of strength that determine a source’s impact:

  • Trans-situational strength – this exists no matter what the situation is, including the source’s age, physical appearance, authority, and perceived intelligence.

  • Situation-specific – this looks closer at the situation at hand and the behavior that the target is being asked to perform.

    For instance, you may be more likely to listen to a doctor when seeking medical advice but may be less likely to take on their interior design advice.


Someone is more likely to influence another if they are close to each other at the time of the influence attempt. There are three types of immediacy:

  • Physical immediacy – how physically close the source is to a target.

  • Temporal immediacy – a target is more likely to be influenced immediately after a source has asked them to do so.

  • Social immediacy – if the source is close friends or family members with the target, they may be more likely to influence them.

    Moreover, if someone is of the same gender, sexual orientation, or religion, they can likely influence each other as they relate to each other.


Simply, this involves the number of people there is in a group. There is a rule called psychosocial law which states that at some point, the number of influencers has less of an effect on the target.

Influence tends to significantly increase up until about 5 or 6 sources are attempting to influence.

Once past 5 or 6 people, the difference in impact increases but at a decreasing rate, meaning it is not as strong.


Numerous studies support the social impact theory. Below are some examples of famous studies:

Sedikides & Jackson (1990)

This was a field experiment that took place at the birdhouse at a zoo. A confederate told groups of visitors not to lean on the railings near the cages that held the birds to see whether the visitors would obey.

It was found that if the confederate was dressed in a zookeeper uniform, obedience was high. If they were dressed casually, obedience was lower.

This demonstrates social impact, especially the strength aspect, because of the perceived authority of the confederate.

As time went on, more visitors started ignoring the instruction not to lean on the railings.

This demonstrates immediacy because as the instruction gets less immediate, it has less of an impact. It was also found that the larger the group of visitors, the more disobedience was observed, which supports the idea of a division of impact.

Darley & Latané (1968) 

This experiment involved participants sitting in booths with the purpose of discussing health issues over an intercom.

One of the speakers was a confederate who would pretend to suffer a heart attack during their talk. It was then observed whether the participants would help the confederate.

It was found that if there was one other participant present, they went for help 85% of the time. This dropped to 62% if there were two other participants and dropped further to 31% if there were 4+ participants.

This study supports Latané’s idea of numbers affecting social impact and the diffusion of responsibility.

You are more likely to help someone if you are the only person present, but there is less responsibility when there are more people present.

Milgram (1965) 

Milgram completed many variations on his original famous experiment wherein ‘teacher’ participants were instructed to administer electric shocks to a ‘learner’ confederate who did not actually receive any shocks.

One variation experiment had two peer confederates in the room with the teacher, who refused to continue the experiment.

The results showed that obedience dropped from 65% to 10% with the presence of two rebelling confederates. This supports that social impact can be influenced by the number of individuals present.

What is dynamic social impact theory?

Social impact theory predicts how sources can influence a target, but a criticism is that it neglects how the target may influence the source.

Social impact theory is now often called dynamic social impact theory as it considers the target’s ability to influence the source. It views influence as a two-way exchange rather than a one-way street.

How does social impact theory relate to social media?

Social impact theory was obviously developed long before social media platforms existed. Nevertheless, social impact theory can be observed and utilized by people and brands to influence others.

If we have friends, family, and co-workers who post on social media, we are more likely to be influenced by their opinions if they are trusted people who are close to us (strength and social immediacy).

Likewise, the number of people who share the same opinion on social media is likely to influence others.

Brands can utilize social impact theory to sell their products on social media platforms. Brands and companies can get people of high status to help promote their products and get people to buy them.

For instance, if we see a celebrity that we like promoting a product on social media, saying how good it is, we may be more influenced to buy the product because of the strength of their influence.

This influence often works best if the influencer is of high status, the influencing statement is more immediate, and there are multiple influencers sharing the same message (strength, immediacy, and number).


Latane, B., & Darley, J. M. (1968). Group inhibition of bystander intervention in emergencies.   Journal of personality and social psychology 10 (3), 215.

Latané, B. (1981). The psychology of social impact.  American Psychologist, 36 (4), 343.

Latané, B., & Wolf, S. (1981). The social impact of majorities and minorities.  Psychological Review 88 (5), 438.

Milgram, S. (1965). Some conditions of obedience and disobedience to authority Human relations 18 (1), 57-76.

Sedikides, C., & Jackson, J. M. (1990). Social impact theory: A field test of source strength, source immediacy and number of targets.  Basic and applied social psychology 11 (3), 273-281.

Saul Mcleod, PhD

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Educator, Researcher

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.

Olivia Guy-Evans

Associate Editor for Simply Psychology

BSc (Hons), Psychology, MSc, Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.