It's also fairly well understood that familiarity plays a role in brand choice. So, you may not care very much about what brand of toothpaste you buy (as an example), but if you're bombarded with advertisements for Crest, you're more likely to pick Crest. The advertisement isn't really meant to get you to go out and buy Crest RIGHT NOW, or even to get you excited about the next time you buy Crest. It's just there to make sure that next time you need toothpaste and are staring at a wall of functionally identical brands, Crest is the first one that jumps into your mind.