Advertising is more effective if seen on multiple platforms

"In the group that was exposed to TV ads alone, 50 percent of people correctly attributed the ad to the correct auto brand. For groups that saw the ad across all screens – TV, computer, smartphone and tablet – the ability to remember the brand jumped dramatically to nearly three-in-four (74%).
Similarly, only 22 percent of the group exposed to just the TV ad was able to correctly remember that the ad was for a 4-door sedan versus 39 percent of the group that saw the ad across all screens."

Source:  Research from Nielsen, commissioned by Google, reported on Nielsen's blog, 29th September 2011