Using a bodily illusion to examine the motivational basis of interoceptive hunger cues.

Internal bodily sensations such as an empty rumbling stomach can lead to enhanced desire for food - hunger. As an empty rumbling stomach is caused by digestive physiology, it is often presumed that such physiological processes also cause hunger. However, psychological processes could equally generate hunger (e.g., based on what the physiological signal has come to connote), and here we outline a method to test this idea. Participants were exposed to a stomach rumbling sound and control conditions (machine sound and silence) while they viewed pictures of food and everyday objects. For each picture, participants evaluated their desire to consume or own it, and judged, if there was a sound, where they felt it came from. Over half the participants experienced an illusion in which they mis-localised the stomach rumble sound to their own body. These participants also judged the pictures of food to be more desirable than comparable food pictures in the control conditions. This effect was obtained irrespective of when they had last eaten. Relative to control conditions, the stomach rumble sound had little impact on desire for pictures of everyday objects. These findings suggest it is possible to generate an illusory interoceptive state independent of physiology, which can then enhance desire to eat. This implies that purely psychological processes can generate bodily-cued desires.