Viewers of both video on demand content delivered via cable boxes and video delivered on the web actually gravitate to longer ad spots, according to a new study by the Atlas Institute, MediaWeek reports (via MediaBuyerPlanner). This goes against the belief that 15-, 10-, or even 5-second ads would become the norm down the road, as advertisers work to capture the short attention spans common to these media.

Atlas found a direct correlation between spot length and the total duration of ad exposure for campaigns. In many cases, while longer spots might drive down the raw number of users who are willing to sit through such ads, the total amount of viewing by those that do chose to watch actually increases with longer spots, since the most engaged viewers end up watching multiple times.

In general, brand exposure was increased by the length of the execution. "When working with short-form video [commercials embedded in other content], push for :30 over :15, :60 over :30. The number of people who will drop-off because of the greater length will be outweighed by the increased time that most spend with your segment," the report advises, ClickZ reports. "In long-form advertising on VOD or Webisodes, strive to lengthen shorter segments with relevant content."