The theory of the spiral of silence is one of the most internationally visible theories of German communication science and was developed in the 1970s by Elisabeth Noelle-Neumann. It is an attempt to describe and ultimately measure processes and functions of public opinion in connection with democratic decision-making processes. In her study, Noelle-Neumann presents five hypotheses that relate to the causes and conditions under which people are willing to express their own opinion publicly - or not. In addition, Noelle-Neumann described the effects of public expressions of opinion and the role of the mass media in this process. The hypotheses were empirically tested through several representative surveys. The spiral of silence explains how minority opinions can become majority opinions in the medium to long term and thus influence political power relations and decisions. Two social psychological phenomena play a crucial role: 1) people’s fear of social isolation and 2) people’s ability to perceive changes in public opinion “quasi-statistically”.