The Cognition of Price

Abstract

Thirsty rats made 10, 30, or 90 licks at an empty spout for 10, 30, or 90 licks at a water spout. In the first experiment, three groups of six experienced a perfect positive, negative, or zero correlation between the number of empty licks required and the consequent number of water licks. The behavioral price of the water lick was the same for all three groups in terms of total empty licks/total water licks. But in terms of the arithmetic mean of the individual prices, the positive correlation imposed the lowest price, the negative correlation the highest. As the mean price increased the rats made fewer water licks, in accordance with the demand law, and licked more efficiently, getting more water per lick. In the second experiment, six rats chose between perfect positive and perfect negative correlational episodes. They showed at best only a slight preference for the positive, 55% on average, but started positive episodes much sooner than negative episodes. In the third experiment five rats chose between an imperfect positive and an imperfect negative correlation that represented a relatively small difference in terms of mean price. They chose each correlation 50% of the time on average, and they started positive episodes no sooner than negative ones. The overall pattern of results suggests that rats code price in terms of the arithmetic mean of the individual prices they have experienced and not in terms of the total cost relative to the total amount consumed over a particular interval of time.