The document summarizes several media effects theories:
1) The hypodermic needle model suggests that media have a direct and powerful influence over audiences' behaviors by "injecting" specific messages that audiences will believe and act on.
2) The inoculation model views audiences as resistant to extreme media messages over time as they become desensitized through repeated exposures.
3) The two-step flow model proposes that media influence flows from media to opinion leaders to the general public, as opinion leaders shape the views of those around them.