Social Influence, Social Perception and Social Behaviour

1A light that only seemed to move

In 1935 the Turkish-American psychologist Muzafer Sherif seated people in a completely dark room and showed them a single, fixed point of light. In total darkness a still light appears to drift, an illusion called the autokinetic effect. Sherif asked each person how far the light moved. Alone, people gave very different answers, some a few centimetres, others much more. Then he tested them in groups of two or three, calling out their estimates aloud. Over a few sessions the estimates moved towards each other until each group had settled on its own shared answer. When people were later tested alone again, they tended to keep the group’s answer.

Nobody had argued, and nobody had been told to agree. Faced with an uncertain situation, people used each other as a source of information, and a group norm was born.

Figure 1. Alone, three people give very different estimates (shaded column); in the group sessions their answers converge on a shared norm.

21. Forms of social influence

In Serge Moscovici’s study, groups of six judged the colour of 36 slides, all of them blue. Two confederates called every slide “green”. When they were consistent, about 8% of the real participants’ answers were “green”, compared with almost none in a control group; when the two were inconsistent, their influence nearly disappeared. A minority changes minds slowly, by being consistent and confident, rather than by pressure.

Influence can also travel through mass media. The economist David Yanagizawa-Drott (2014) compared Rwandan villages that could and could not receive the extremist radio station RTLM in 1994, because hills blocked the signal in some places. He estimated that about one in ten acts of participation in the violence of the 1994 Genocide against the Tutsi could be linked to the broadcasts. The study is an estimate built on geography and court records, not a laboratory experiment, but it shows that words broadcast to a whole population can change what ordinary people do.

32. Social perception: forming impressions

In 1946 Solomon Asch gave students a list of traits describing an imaginary person: intelligent, skilful, industrious, warm, determined, practical, cautious. Another group read the same list with cold instead of warm. The “warm” person was judged generous, happy and humorous far more often than the “cold” one. Swapping polite and blunt made little difference. Asch concluded that some traits are central: they colour how we read all the others.

In 1950 Harold Kelley tested this with a real guest lecturer at an American university. Before he arrived, students read a short note describing him as “rather warm” or “rather cold”. After the same 20-minute discussion, the “warm” group rated him more favourably, and more of them joined in the discussion (56% against 32%).

Other biases in social perception include the primacy effect (early information outweighs later information) and the halo effect (one good trait, such as attractiveness or fluent speech, makes us assume others).

43. Social behaviour: when do bystanders help?

Laboratory studies since the 1960s found the bystander effect: the more people present, the less likely any one of them is to help. But a 2011 review of 105 studies by Peter Fischer and colleagues found the effect is weaker in clearly dangerous emergencies. In 2020 Richard Philpot and colleagues examined CCTV recordings of 219 real arguments and fights in Amsterdam (the Netherlands), Lancaster (the United Kingdom) and Cape Town (South Africa). In about nine out of ten, at least one bystander stepped in, and the more bystanders there were, the more likely it was that someone helped. Each individual may be less likely to act in a crowd, but a crowd contains more potential helpers.