According to Agner Fog, mass media has a profound influence when it comes to setting an agenda and priming people on new issues. Mass media can also affect people's opinions about various topics, which may lead to biased judgments .
The influence of mass media has grown as the number of media outlets and communication channels has increased. Traditionally, news and information was delivered in newspapers, radio and TV, but technological advancements, such as the Internet and mobile technology, have impacted the way people access mass media. As a result, people are exposed to the opinion of the mass media on a daily basis, which affects their values and norms over time. Studies have found that the mass media does not change people's opinions on issues for which they already have a strong opinion, but it does have an effect on the extent to which people believe in new ideas or options. People use the media to learn about current events and historical facts because the media presents itself as a credible authority. Media companies that own major television and radio broadcasting stations control the messages across all media outlets and use imagery to influence the people's decisions through advertising.