All right, a little argument. The title overstates it, but by less than you might think, and the research is clear about where humour earns its keep and where it quietly costs you.
What the evidence says
The largest review of the question, Martin Eisend's 2009 meta-analysis of humour in advertising in the Journal of the Academy of Marketing Science, pooled decades of studies. Its clearest findings: humour reliably wins attention and makes people like the ad. Its effects on what people think of the brand, and on whether they buy, are weaker and less certain. An earlier review by Weinberger and Gulas (1992) came to a similar view, and found that humour related to the product tends to work better than humour that is not.
So humour is a superb way to be noticed and liked. On its own, it is not a way to be chosen.
Why that matters for entertainment marketing
Entertainment has an advantage most categories lack: the product is itself an experience of feeling. A comedy trailer that makes you laugh is not decoration; it is a sample of the film. The joke and the product are the same thing, which is exactly the related humour the research favours.
Make the joke the product. A laugh drawn from the film's own characters and situations sells the film; a laugh borrowed from elsewhere sells the laugh.
Keep the genre's promise. Humour in a horror campaign can work as release, but it must not break the dread the audience is paying for.
Plan for wear-out. A joke that delights on the first view can grate by the tenth. Plan a rotation, not a single gag.
Know who is laughing. Humour is the most audience-specific tool there is. What delights one segment alienates another, so the joke has to be built on what this audience already believes about itself.
The short version
Humour is the fastest route to attention and goodwill, and in entertainment, where the feeling is the product, it can be the most persuasive tool in the box. Used well, it comes close to the most effective strategy. Used carelessly, it is the most expensive way to be forgotten. Argue with that.
Arcanamatic's Campaign Psychology Audit works out what an audience will laugh at, and why, before the campaign is cut. See the packages.
