Social Impact Theory

Principles of Social Impact Theory

The first principle of the theory, the principle of social forces, is expressed mathematically as follows: î = f(SIN), where î stands for the magnitude of social impact, f is a function, S is strength of the sources, I is immediacy (e.g., closeness in space or time), and N is number of sources. Strength includes such things as the salience or importance of a source and may be operationally defined by manipulating such source variables as authority, socioeconomic status, or expertise. Immediacy can be thought of as the ease with which a message may be communicated, and it is often operationally defined as physical proximity. Number is simply how many sources of social influence there are. As strength, immediacy, and number of sources of social influence increase, the magnitude of social impact on a target is expected to increase. The proposed multiplicative relationship implies that if any one of the three parameters (strength, immediacy, or number) is zero, no social impact will occur.

The second principle of the theory, the psychosocial law, is expressed as follows: î = sNt, t < 1, where î = the magnitude of social impact, s is a scaling constant, N is the number of sources, and t is an exponent with a value less than 1. Conceptually, the psychosocial law was modeled after S. S. Stevens's psychophysical law, which proposed that the subjective psychological intensity of a stimulus increases as the objective intensity increases, but it follows a law of diminishing returns. That is, each new source adds additional pressure to change a target's thoughts, feelings, or behavior, but the social impact of each new source adds less and less pressure to change. For example, the first source (increasing from 0 to 1) has more impact than the sixth (increasing from 5 to 6).

Research on conformity provides mixed support for the psychosocial law. In Solomon Asch's classic studies, the first source of influence resulted in very little conformity. Instead, the largest increase in conformity occurred when the number of sources was increased from two to three. Later conformity research, including Stanley Milgram's research in which confederates stood on a street corner in Manhattan and looked up at the sixth floor of a building, provides support for the psychosocial law, which predicts diminishing returns as the number of sources increases. Other research, including work on stage fright and the perceived importance of news events, also supports the predictions of the psychosocial law. In studies of stage [Page 806]fright, for example, as perceived audience size increased from 1 through 16, participants rated their subjective tension to increase as a predicted power function of the size of the audience. Increasing the strength of the audience (age given as either early teens or late 30s) similarly increased the subjective tension experienced by participants.

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