This week, the Conservatives, Liberals, and NDP all debuted new television ads for their respective parties.

For the most part, they were positive affairs, focusing on the favourable qualities of each party's leader. One could be considered a "negative" ad. From the Conservative Party, it depicts a focus group discussing Liberal Leader Justin Trudeau. The group each announces questions or concerns they have over Trudeau's policies and experience.

Opinion polling in Canada has shown that voters say they don't like negative ads, so many people might be happy with this week's 3:1 ratio of positive to negative ads. However, some research suggests that negative campaigns and ads are a benefit to democracy, and do more to inform and help voters than positive ads.

David Redlawsk is a political psychologist and Professor at Rutgers University in New Jersey. He is co-author of the new book "The Positive Case for Negative Campaigning." He says viewers get more, and better information from negative ads than positive ones.

Voting is about information. It's about learning something about your options. And without any kind of negativity, those options aren't complete. No candidate, no party is ever going to tell you something bad about themselves, so it requires someone else to do it. - David Redlawsk, Professor of Political Science, Rutgers University

So if negative ads are useful, why do people dislike them? Redlawsk says the reaction is more to do with the connotations of the word "negative.

We aren't supposed to like something that's negative. On the other hand, when we ask voters questions that get at the core of negativity, that is, talking about an opponent, challenging an opponent, we find that if we don't use the word "negativity" voters are much more supportive. They actually do want to learn about both sides. - David Redlawsk, Professor of Political Science, Rutgers University

Redlawsk says that of the negative Canadian political ads he's seen, they're rather tame by American standards.