Has the lure of naughty food sometimes felt so intense that your only chance of resistance would be to tie your hands down? If so, take comfort: A new study in Brain and Cognition suggests that this is all just part of being human. The researchers at the International School for Advanced Studies in Italy found that pictures of food (by virtue of their “high motivational value”) exert an automatic pull on people’s reaching movements, literally drawing their hands closer to temptation.
Dr. Francesco Foroni recruited 57 young men and women of normal weight (they weren’t particularly hungry at the time of the experiment, either) to perform a simple task on a tablet computer. They had to use a stylus to draw a line as quickly as possible from one green dot near the bottom of the screen toward another green dot near the top, 13 centimeters away. Every trial there was a distracting picture on one side or the other of the target dot, either of a natural food item like a banana, a processed food item such as a pizza, or a kitchen tool, such as a toaster or knife (the processed and non-processed foods were matched for caloric content). The participants also rated all the different foods on a number of dimensions, such as how much they liked each item and how healthy they thought it was, and they said how hungry they were and whether they were dieting. Finally, they completed a test of their subconscious feelings about the foods, based on how readily they associated the foods with positive and negative words.
The researchers analyzed the trajectory of the lines that their participants drew between the dots and found clear evidence that their movements were attracted toward the food and food-related pictures, bending toward them, away from the optimal path between the two dots. The participants always reached the target dot, but at a subconscious level their hand movements were drawn toward the food pictures, like a swimmer pulled by a powerful current.
According to the researchers, this finding reinforces the idea that “food and food-related stimuli are powerful attentional-capturing cues and strong sources of interference with ongoing actions even if irrelevant to the task.” This is a scientific way of saying their results are consistent with the way it so often feels like food is calling out “Eat me! eat me!”
The food-attraction effect was found for both men and women and wasn’t associated with the participants’ BMI, nor whether they were dieting. However, the strength of the pull of the food pictures wasn’t always the same. The researchers found that the more unhealthy a given participant perceived a given processed food item to be, and the more negatively they felt about it at a subconscious level, the stronger a pull these food items exerted on the participants’ hand movements.
Foroni and her colleagues speculated that this effect occurred because people who have negative attitudes toward processed food actually see these kinds of foods on a subconscious level as “dangerous.” We’re wired to pay rapid attention to danger, they say (just think how our attention is grabbed by snakes and spiders), and so, paradoxically, those people who had a more negative attitude to processed food were actually drawn to it more powerfully. This does have the ring of some pretty convenient post-hoc reasoning (wouldn’t it make more sense to move your hand away from danger?), but if the researchers are right, no wonder so many diets end in failure — the results suggest that the more you see naughty food as a “threat,” the more your hand’s going to be drawn to it.
This new research isn’t the first to show that food has a powerful attention-grabbing effect: We already know that food imagery gives the hungry brain a kick, and that it attracts people’s gaze, especially when it’s highly calorific. But this study takes things further, demonstrating its subconscious influence on people’s actual reaching movements. In fact, the researchers think their study may have underestimated the size of this effect — after all, they noted, their participants weren’t particularly hungry and the food pictures kept appearing in predictable locations, which should have made them easier to ignore. When you’re hungry and your guard is down — think of an office colleague suddenly appearing by your side with an offer of some birthday cake — it’s no wonder your hand somehow seems to reach out of its own accord.
Dr. Christian Jarrett (@Psych_Writer), a Science of Us contributing writer, is editor of the British Psychological Society’s Research Digest blog. His latest book is Great Myths of the Brain.