“Even stranger than our teeth-brushing behaviour is our preference for stripy toothpaste. When it first appeared, in a product called Stripe, it aroused a great deal of debate over how it was made. Many people dissected the empty container; others froze a full tube and then cut it open in a cross section.* What was strange was that nobody ever asked ‘Why?’ After all, the moment toothpaste enters your mouth, all the ingredients are mixed together, so what was the point of keeping them separate in the tube? There are two explanations: 1) simple childish novelty and 2) psycho-logic. Psychologically, the stripes serve as a signal: a claim that a toothpaste performed more than one function (fighting cavities, tackling infection and freshening breath) was thought to be more convincing if the toothpaste contained three visibly separate active ingredients. In general, people are impressed by any visible extra effort that goes into a product: if you simply say ‘this washing powder is better than our old powder’, it is a hollow claim. However, if you replace the powder with a gel, a tablet or some other form, the cost and effort which have gone into the change make it more plausible to the purchaser there may have been some real innovation in the new contents.”