Greater effort boosts the affective taste properties of food

Actions can create preferences, increasing the value ascribed to commodities acquired at greater cost. This behavioural finding has been observed in a variety of species; however, the causal factors underlying the phenomenon are relatively unknown. We sought to develop a behavioural platform to examine the relationship between effort and reinforcer value in mice trained under demanding or lenient schedules of reinforcement to obtain food. In the initial experiment, expenditure of effort enhanced the value of the associated food via relatively lasting changes in its hedonic attributes, promoting an acquired preference for these reinforcers when tested outside of the training environment. Moreover, otherwise neutral cues associated with those reinforcers during training similarly acquired greater reinforcing value, as assessed under conditioned reinforcement. In a separate experiment, expenditure of effort was also capable of enhancing the value of less-preferred low-caloric reinforcers. Analysis of licking microstructure revealed the basis for this increased valuation was, in part, due to increased palatability of the associated reinforcer. This change in the hedonic taste properties of the food can not only serve as a basis for preference, but also guide decision-making and foraging behaviour by coordinating a potentially adaptive repertoire of incentive motivation, goal-directed action and consumption.