Generalization of appetitive conditioned responses

Abstract

A stimulus (conditioned stimulus, CS) associated with an appetitive unconditioned stimulus (US) acquires positive properties and elicits appetitive conditioned responses (CR). Such associative learning has been examined extensively in animals with food as the US, and results are used to explain psychopathologies (e.g., substance‐related disorders or obesity). Human studies on appetitive conditioning exist, too, but we still know little about generalization processes. Understanding these processes may explain why stimuli not associated with a drug, for instance, can elicit craving. Forty‐seven hungry participants underwent an appetitive conditioning protocol during which one of two circles with different diameters (CS+) became associated with an appetitive US (chocolate or salty pretzel, according to participants’ preference) but never the other circle (CS−). During generalization, US were delivered twice and the two CS were presented again plus four circles (generalization stimuli, GS) with gradually increasing diameters from CS− to CS+. We found successful appetitive conditioning as reflected in appetitive subjective ratings (positive valence, higher contingency) and physiological responses (startle attenuation and larger skin conductance responses) to CS+ versus CS−, and, importantly, both measures confirmed generalization as indicated by generalization gradients. Small changes in CS‐US contingency during generalization may have weakened generalization processes on the physiological level. Considering that appetitive conditioned responses can be generalized to non‐US‐associated stimuli, a next important step would be to investigate risk factors that mediate overgeneralization.

Abstract

Numerous studies demonstrated overgeneralization of conditioned fear as a pathological marker for anxiety disorders as well as stress‐related disorders. Appetitive conditioning is crucially involved in mental disorders such as eating or substance‐related and addictive disorders. Thus far, the generalization processes of appetitive conditioned responses remain unexplored. In this study, we demonstrate for the first time a generalization gradient of appetitive conditioned responses. Our study contributes and extends the understanding of generalization processes by explaining, for instance, why craving can be elicited by stimuli that share physical properties with a stimulus signaling the drug.