The advertising doesn't simply need to affect your personal preferences to affect your buying habits. If you were buying a few different packs of soda for a gr

The advertising doesn't simply need to affect your personal preferences to affect your buying habits. If you were buying a few different packs of soda for a group of people (e.g. for a party), how much cheaper would the case of Pepsi need to be than a case of Coke for you to buy it instead? Could that be affected by advertising that made you feel like, regardless of your personal affinity for Coke, Pepsi is the acceptable default choice? Imagine further that this isn't a product category that you feel quite so strongly about (most people don't have a 4-deep ordered list of brand preferences for common product categories). If you were making a quick choice between Sprite and 7-up (again, for a party), are you sure that advertising couldn't possibly influence which of the brands is most accessible to your brain?