The two-step flow of communication model says that most people form their opinions under the influence of opinion leaders, who in turn are influenced by the mass media. In contrast to the one-step flow of the hypodermic needle model or magic bullet theory, which holds that people are directly influenced by mass media, according to the two-step flow model, ideas flow from mass media to opinion leaders, and from them to a wider population.
The theory is based on a 1940s study on social influence that states that media effects are indirectly established through the personal influence of opinion leaders. The majority of people receive much of their information and are influenced by the media secondhand, through the personal influence of opinion leaders.
The two-step model says that most people are not directly influenced by mass media, but that they rather form their opinions based on opinion leaders who interpret media messages and put them into context. Opinion leaders are those initially exposed to a specific media content, and who interpret it based on their own opinion. They then begin to infiltrate these opinions through the general public who become "opinion followers". These "opinion leaders" gain their influence through more elite media as opposed to mainstream mass media. In this process, social influence is created and adjusted by the ideals and opinions of each specific "elite media" group, and by these media group's opposing ideals and opinions and in combination with popular mass media sources. Therefore, the leading influence in these opinions is primarily a social persuasion.
The two-step flow of communication model hypothesizes that ideas flow from mass media to opinion leaders, and from them to a wider population. It was first introduced by sociologist Paul Lazarsfeld et al. in 1944 and elaborated by Elihu Katz and Lazarsfeld in 1955 and subsequent publications. Lowery and DeFleur argue the book was much more than a simple research report: it was an effort to interpret the authors' research within a framework of conceptual schemes, theoretical issues, and research findings drawn broadly from the scientific study of small groups Unlike the hypodermic needle model, which considers mass media effects to be direct, the two-step flow model stresses human agency.