One of the effects of advertising is to modify the nature of the communication media where it is shown. The most clear example is television. Channels that get most of their revenues from publicity try to make their medium a good place for communicating ads. That means trying to make the public stay for long times and in a mental state that will make spectators not to switch the channel through the ads. Programs that are low in mental stimulus and require light concentration and are varied are best for long sitting times and make for much easier emotional jumps to ads, that can become more entertaining than regular shows. A simple way to understand the objectives in television programming is to compare contents from channels paid and chosen by the viewer with channels that get their income mainly from advertisements.