It's not exactly a shock that looking at images of high-calorie foods might make you suddenly crave a pizza. But based on a recent study in the open access journal PLoS ONE, if you're eating one food while looking at images of various high-calorie foods, you'll think the food you're eating tastes better.
In the study, 14 participants between the ages of 22-30 were presented 150 photographs -- 100 were food items and 50 were non-food kitchen utensils. They were simply told to identify the photographs as food or non-food. An electrode (referred to as a "taste stimulus") was placed on the participant's tongue so the researchers could monitor brain activity in response to the photographs. Based on the brain response connected with the electrode, the stimuli were perceived more pleasant when preceded by images of high-calorie food, as compared to low-calorie food. The participants were blind to this fact -- they were merely categorizing photos.
The study authors, led by Johannes le Coutre of the Nestle Research Center in Switzerland, concluded, "When viewing high-calorie food images, participants reported the subsequent taste to be more pleasant than when low-calorie food images preceded the identical taste."
Based on these results, it seems as if you have a solution for that bland sandwich you're eating. Just look at images of high-calorie foods at the same time and it might suddenly taste better.