New York: In order to create viral YouTube ads, brands should arouse strong emotion, keep ads to a moderate length of 1-1.5 minutes and use authentic characters, a study has revealed.

YouTube is a low-cost and flexible platform for sharing ads with a wide viewership.

According to the study published in the Journal of Marketing, a brand should create an ad with a captivating plot, a surprise ending and authentic characters.

"Our findings provide marketing and media managers, advertisers and copy writers with specific theory-based insights into how to design ads to drive virality," said study author Gerard J. Tellis, Professor at the University of Southern California in the US.

For the study, the researchers included 109 brands that were among the top 100 US advertisers in 2012 as well as additional brands that were historically active on YouTube.

It was found that ads that evoke positive emotions of inspiration, warmth, amusement and excitement stimulate strong positive sharing. Ads that use drama, plot, surprise and characters such as celebrities, babies and animals evoke emotions and induce sharing.

Advertisements with length between 1.2 and 1.7 minutes are the most shared, said the researchers.

"We find that minimal brand exposure, discreet information, and strong emotion are key drivers of virality," Tellis said.