​The first thing I learnt from Gordon Brown (one of the founders of research company Millward Brown, not the PM), was that people don’t pay much attention to advertising. They only notice and remember certain elements/moments/aspects of ads i.e. the (few) bits they find interesting, entertaining or emotionally compelling. They ignore or quickly forget everything else - sometimes the whole ad.
 
This is why the best way to find out whether your ad is effective or not is to establish what, if anything, people find memorable about it. Then you need to determine whether the things people do remember are connected to the brand and intended message. This useful framework has been referred to as the 'Creative Magnifier/V-diagram’ (Millward Brown) and relates directly to the 'ABC’ of ad effectiveness (Unilever’s acronym following 'SMILE’).