DOES PACKAGE SIZE MATTER? A UNIT‐PRICE ANALYSIS OF “DEMAND” FOR FOOD IN BABOONS

In a study examining “demand” for food, responding of 8 adult male baboons ( Papio c. anubis ) was maintained under a fixed‐ratio schedule of food reinforcement during daily 23‐hr experimental sessions. Completion of the ratio requirement resulted in the delivery of one, five, or 10 1‐g food pellets. Supplemental feeding was limited to fruit and a dog biscuit daily. Responding increased as “cost” was increased across a wide range of fixed‐ratio values before reaching a maximum and then decreasing. Increasing the number of food pellets per delivery decreased total responding and the number of reinforcements per day. A unit‐price analysis, in which intake was converted to grams per day and fixed‐ratio values were converted to responses per gram, yielded demand functions that overlapped at lower unit prices. Under one or more multiple‐pellet conditions, however, intake decreased more quickly than under the one‐pellet condition as the fixed‐ratio value was increased in all but 1 baboon. This indicates that even when using unit‐price conversions, there was variability in total intake. Although unit‐price conversions yielded intake data that were more consistent across conditions, conditions differed in response topography even at the same unit prices: Under the multiple‐pellet conditions there were longer pauses in responding, running response rate was slower, and the first eating bout (i.e., “meal”) of the session was smaller than under the one‐pellet condition. These findings (a) support the heuristic value of a unit‐price analysis for studying responding for and consumption of commodities that have similar attributes, and (b) indicate that different response topographies may result in similar intakes of a commodity.