YouTube users are 1.5 times more engaged in advertising than TV viewers

"YouTube users are 1.5 times more attentive and engaged in advertising than TV viewers, according to research conducted in partnership with General Motors Europe, Motorola, media agency MindShare and the Online Testing Exchange (OTX)
The research used eye tracking and biometric data to reveal the brand impact of advertising on YouTube. It found recall and attribution for an ad viewed was up to 14% higher than watching the same ad on TV. Viewing a silent ad on YouTube in addition to a normal TV ad also improved ad recall and attribution.
Ads on YouTube can impact the perceptions of elusive audiences like young men and infrequent TV viewers. They also have a halo effect and increase brand perceptions such as innovative, cool, dynamic and unconventional."
Source: NewMediaAge, 18th December 2008, citing research commissioned by YouTube (yes, ok), conducted by OTX.
See also the comment underneath the article from Tess Alps at Thinkbox, questioning the research.