Food deprivation reduces the susceptibility to size-contrast illusions.

Hunger, caused by mild amount of food deprivation, is an everyday physiological state familiar to us all. Ongoing research has pinpointed the way hunger affects people's physiological functions as well as their attitudes and allocation of attention toward domain-specific, food-related objects. Yet, little is known about the way food deprivation affects basic perceptual abilities. Here, we utilized size-contrast visual illusions commonly associated with food to explore the way deprivation affects relative processing of food size. In two experiments (Nexp1 = 32 females, mean age: 24.31; Nexpt2 = 41 females, 40 males, mean age: 23.84), we examined the effect food deprivation has on participants' susceptibility to the Delboeuf illusion, which biases the perceived size of a neutral or of a food-related object when it is placed within the context of another object (e.g., a pizza is perceived as smaller when placed on a larger plate or tray). The results showed that food deprivation reduces the illusory bias for food-related but not for neutral stimuli. Such reduction in the illusory effect indicates reliance on analytic, rather than on relative processing style, for domain-specific stimuli when in the state of hunger.