The rat's sweet tooth

In 1974 D. G. Mook reported that rats do not seem to have a sweet tooth (Psychological Review, 81, 475-490). Although rats preferred saccharin-flavored water over plain, they did not prefer saccharin-flavored foods over plain. He suggested sweetness elicits consumption only when it is nonredundant cue signaling a substance is to be eaten. Here we found rats do indeed prefer many sweetened foods over plain. They preferred sucrose-flavored mash to plain mash, sucrose-flavored potatoes to plain potatoes, and sucrose-flavored potatoes to polycose potatoes. In general, rats preferred sucrose-flavored foods to plain foods even when calories were equated between the foods. Also, they liked saccharin-flavored milk and saccharin-flavored mash when saccharin concentration was low. When concentration of saccharin was high, they disliked saccharin-flavored mash more than they disliked saccharin-flavored milk. We suggested the hedonic or perceptual reaction to sweet depends on what other substances accompany the sweet, so that some foods and liquids taste better sweetened, others taste better unsweetened. Rats generally like sucrose-flavored food and seem to like saccharin better in liquid food than in solid. Perhaps the bitter taste of saccharin is accentuated in solid foods. Also, experience with saccharin increases the preference for it. Future research should be directed to how other food elements act in concentration with various sweeteners to determine the perceptual and hedonic reaction to sweetened foods.