During that time some 2,500 books and articles have been written on the effects of TV and film violence on human behavior.

Although the concern in Canada was primarily violence (hence the V-chip), in the United States there is also great concern about sexual content -- probably more than in most other industrialized societies.

Hence, the V-chip can be programmed to screen out both violence and sex.

A clear cause-effect relationship between media violence and violence in society is complicated by the fact that children are typically exposed to many stimuli as they grow up, many of which could play a role in later behavior.

For example, during a child's life we can't discount the role of such things as violent video games, the social values of parents and peers, or general living conditions.

Boys who grew up watching violent TV shows were more likely to be violent with their wives.

Researchers concluded in Developmental Psychology that, "Every violent TV show increases a little-bit the likelihood of a child growing up to behave more aggressively." We'll look at more of the research in a moment.

Canada was one of the first countries to extensively research this issue.

The results of their studies prompted some of their engineers to devise the "V-Chip." As you may know, the V-Chip allows parents to lock out TV programming they consider objectionable to their children.

If you eat something that you have not tried before and immediately get sick, you will probably assume there's a direct relationship between the two.

And if at some later date you forget about your first experience and eat the same thing again, and immediately get sick again, you can be fairly sure that whatever you ate makes you sick.

No rocket science here, just clear cause and effect.