[Optimization of behavior by minimization of displeasure in a 2-dimensional sensory space]

Three healthy young adult males were placed on a treadmill geared to five speeds and five slopes in combination. At minute 16 they gave estimates of displeasure for sensations aroused in their chest and lower limbs. These estimates were compared to the operant choice of the subjects when they were given the task, in other sessions, of climbing up 300 m on the treadmill at varying speeds and slopes. When speed was imposed, they could adjust slope and reciprocally. The were instructed that the session would end when they had reached the 300 m elevation. The results showed that the subjects adjusted slope and speed inversally; time for climbing up 300 m was almost constant, i.e. they tended to work at constant power in various conditions. Such performance could be predicted from the sum of ratings of displeasure aroused in the lower limbs and in the chest. These results suggest that optimalization of behaviour was obtained by minimization of bidimensional displeasure.