The Cabletelevision Advertising Bureau released a study today that found that ad engagement was lower on smaller screen devices. Consumers said the maximum length of ad they would watch on mobile phones is nine seconds, compared to 42 seconds on TV. Nearly half of respondents said they didn’t want advertising on alternative devices and more than half said they didn’t want to pay for content in exchange for skipping ads on smaller-screen devices.

The study also found that 21 percent of people say watching video on the computer was a primary function of the device. Those same respondents ranked the computer first among devices they couldn’t live without, with TV second. Mobile phones were third.