Social Impact Theory

Social impact theory was developed by Latane to describe how we behave within 'social forcefields' through our interactions.

The person doing the influencing is labelled the 'source' and the person being influenced is labelled the 'target'. Latane produced a mathematical formula to represent his theory about how 'sources' impact 'targets'

I = f[SIN]
impact on the target is a function of strength mutiplied by immediacy multiplied by number of sources

The formula indicates how three key factors (strength, immediacy and number) predict how the target will change their thoughts, feelings and actions. Strength refers to the percieved power/authority of the source and the messages that they communicate (for example the source may have power over the target and/or communicate in an authoritative or charismatic way). Immediacy reflects the closeness of the source and target in terms of phsyical and psychological distance. And number relates to how many sources are present during the interaction, which determines the level of social impact.

Latane used the phrase multiplicative effect to explain how increasing strength, immediacy and/ or numver of sources can significantly increase the social impact. The divisional effect explains the idea that social impact is reduced if there are more targets than there are sources - the impact is divided by the number of targets therefore the impact on each person is reduced.

Latane stated that once the source group was bigger than 3, each additional person has less of an influencing effect. such as adding one extra person to a group of 52 would have less of a social impact than adding one person to a group of two - this is called the law of diminishing returns.

Milgram's variation #7 (telephonic instructions) provides evidence for social impact theory. Milgram found that only 9/40 (22.5%) of ppts were fully obedient when given instructions over a phone rather than having the auhtority present. ppts also lied on the phone saying they were raising the shock level when they had not. When the researcher came back into the room the defiant ppts became obedient again. This shows that the immediacy of the source affected obedience rates as the source was not physically in the room but when the source returned, obedience increased. Therefore, this supports social impact theory making it possible to trust in the credibility of this theory and apply it to understanding obedience in real life situations, for example the Mei lai massacre (where blind obedience led to the death of innocent civillians).

A weakness of social impact theory isthat the role of immediacy may not be a key ingredient in social impact. Hofling et al (1966) arranged for an unknown doctor to telephone 22 nurses and ask each of them to administer an overdose of a drug - 95% of the nurses started to administer the drug (they were prevented from doing so). This challenges social impact theory because the sources being absent should have reduced obedience but it didn't.

This study didn't have any kind of control group to create a baseline for how much more or less obedience was effected by the immediacy of the doctor.

social impact theory could be seen as reductionist. it reduces the complexity of human thoughts, feelings and experiences to three numbers in order to predict the outcomes. Qualifying 'strength' in particular is difficult because it is a subjective to the sources and targets involved. This suggests that, in order for social impact theory to make accurate predictions, it may be necessary to gather qualitative data to better understand how the targets and sources perceive each other.

social impact theory can be easily applied to understand how people enhance their social influence. For example, political leaders may increase their influence by (1) adopting a strong and persuasive style of communication (2) talking face to face with voters (3) addressing smaller groups to avoid divisional effects. This shows how this theory can be applied to society and how people's behaviour could be influences through a strategic campaign

brief outline
sources + targets / supporting study
SIN / reductionist
law of diminishing returns / criticism / CA (internal val)
multiplicative + divisional effects / application