Nov. 29, 2011 at 9:02 AM ET
Mom's lasagna. Homemade chocolate chip cookies straight from the oven. Steak sizzling on the grill. Roasted turkey and stuffing. Flame-broiled hamburgers. Good-quality dark chocolate.
Is your mouth watering at the very thought of some of these foods? Sorry to break it to you, but a recent study found that humans are not able to salivate at the thought of food.
"We are not like dogs -- in particular, we're not like Pavlov's dogs -- and don't have conditioned salivary reflexes," says lead author Guy Carpenter.
In the small study, published in the Journal of Texture Studies, British researchers tried to determine if a mouthwatering sensation exists in humans at the suggestion of food. They rounded up 5 healthy people and first showed them pictures of different foods -- from pizza and Thai curry to grilled chicken and baked pasta.
Using cotton pads inside the cheeks and suction devices under the tongue, scientists collected saliva samples from participants as they viewed this visual feast.
Looking at photographs, which simulates thinking about food in real life, didn't increase the amount of saliva flowing from any of the major salivary glands, before or after eating a meal. In other words, a "mouthwatering sensation" wasn't seen in the participants whether they were hungry or not.
Although food advertisers may want consumers to believe that pictures of food can have a mouthwatering influence, this study found it wasn't the case.
In another experiment, researchers observed how much moisture the mouth produced when volunteers could see and smell a bowl of hot noodles. And a third test, gathered saliva samples before, during, and after participants ate their lunch.
Smelling food's aromas increased saliva secretions more so than holding food or looking at pictures of it. But the largest quantities of spit flowed when participants actually tasted and chewed food.
"This study reinforces the idea that merely thinking of food doesn't cause a faster rate of saliva into the mouth," says Carpenter, a senior lecturer in oral and mucosal biology at King's College London Dental Institute.
Mouthwatering, he says, is not a true salivary reflex, meaning a stimuli that can increase saliva secretion for prolonged periods. Instead Carpenter proposes the mouthwatering sensation "is due to small squirts of saliva entering the mouth when facial muscles squeeze on dilated salivary ducts."
Carpenter says "to increase the anticipation and mouthwatering aspect" of a meal, "increase the smells."
Readers, tell us what are the food smells that always make your mouth water?