1 A situation in which two or more individuals are engaged in the same activity at the same time. The general affect of coaction is to raise arousal levels. Individuals who are optimally aroused for a sporting event may become overaroused when joined by other individuals. This may lead competitors to perform less well and spectators to become aggressive. The larger the number of people engaged in an activity and the closer their proximity to one another, the greater the coaction effects will be.
2 The interaction between two or more individuals, which produces a motivating effect on performance. Compare audience effect, social facilitation. See also dynamogeny, social interactive forces.