The general conclusion seems to be that emotion is stronger than rational arguments in selling your brand. Often you need both, but emotion is the key.
There has also been extensive research in the related area of emotion in memory, which is important because if you don't retain the message, what good is it? Here the research really gets interesting. Generally speaking, we remember emotional events better than routine ones. (The three most important words in the English language are usually whispered: "I love you". Somehow we tend to remember where and when they were spoken, even though we may not remember finishing our chai latte this morning.)
Drilling down even further, current research indicates that it's which emotions are aroused, not the event, that matters to our memories.
Good memories tend to fade faster, and the bad ones haunt us.
All of this relates to advertising and marketing. If the emotion aroused is relevant to the product and its benefits, it's remembered better. If the emotional part of the commercial comes after the information is delivered, it can wipe out the message we want consumers to retain.
Humor works well when the humor is about the product and its benefits. The same with scary commercials. When the scary part is just borrowed interest, it doesn't help us remember about the product. We're too smart; our brains push the delete buttons.
Another variable: your mood at the time you receive the messages. If you're watching an intense program on tv and the commercial comes on, you'll probably mentally pull away. A dull show? The commercial might be the most colorful, emotional part, and has a better chance of being engaging.
These are generalities, of course, but they all add up to one central theme: truly understanding how the customer responds is where it all begins. Which is why you'd better re-read this.