Social mood is the engine of social action. It is always present. Social mood governs the character of social events. Neurologically, social mood is manifested via the herding impulse in the amygdala, a part of the limbic system.
Social mood waxes and wanes positively and negatively. A positive social mood is associated with a host of social phenomena, such as bull markets, bright colors, short skirts, re-election of incumbents, peace, and deregulation. A negative social mood is also associated with a host of social phenomena, such as bear markets, dark colors, falling hemlines, rejection of incumbents, discord, and regulation.
A subtle but important point: Although social mood governs social events, it fluctuates independently of such events. In other words, wherever mood goes, events will follow. But, the events themselves have no impact on the direction of social mood; there is no feedback loop. If social mood governs social events, what governs social mood? Answer: The Wave Principle.
When we say social mood determines the character of social events, we mean is that the mood determines the general type of events that will emerge, but not the specific events themselves, nor the actions of specific individuals. Here is an example: Socionomic theory predicts that during times of negative social mood, horror movies will be popular. However, we cannot say whether or not a movie studio will green light the feature-length production of a particular horror film. Nor can we say—if the film gets made—that a specific individual will see the movie at his local cineplex.
Courtesy of the Socionomics Institute, http://www.socionomics.net/2011/04/social-mood/