The hypodermic needle model of communication, also known as the magic bullet theory, suggests that media messages have a direct and uniform effect on passive audiences similar to injecting a hypodermic needle (i.e. direct injection). This model from the 1930s views audiences as directly influenced by media messages without personal interpretation. However, Katz and Lazarsfeld's two-step flow of communication model from 1955 found that media messages are often interpreted by opinion leaders in social groups before reaching others, challenging the notion of direct media effects.