Effects of response requirement and reinforcer delay on pigeons' demand for food in a closed economy

In behavioral economics, unit price is commonly defined as a cost-benefit ratio of response requirements and reinforcer magnitude. My study compared the effects of work- and delay-based price on pigeons' consumption of food in a closed economy. Previous research found that work- and delay-based demand curves sloped downward and overlapped, suggesting that the work-based decrease in consumption was primarily due to associated delays. My study extended previous research by examining a wider range of work requirements and by varying reinforcer magnitude.;Work requirements were defined as a fixed number of pecks on a key, and reinforcer magnitude was defined as timed access to grain. In Part 1, pigeons were exposed to a series of work-based unit prices ranging from 6.25 to 200 (responses per unit food delivery). Unit prices were arranged by combining fixed-ratio schedules (12 to 1600) with reinforcer magnitudes (2-, 4-, and 8-s food access). In Part 2, the delay equivalents of the ratio schedules from Part 1 were presented via response-initiated fixed-interval schedules. Under these schedules, a key peck initiated and terminated a fixed delay to food. The interval schedules were based on individual ratio-completion times from Part 1 (i.e., delays were yoked within subjects). Under low to moderate prices, ratio and yoked-interval demand curves both sloped downward and converged. Under the highest prices, ratio demand curves continued to decrease but yoked-interval demand curves sloped upward. This increase in consumption at the longest delays was related to a concomitant decrease in the number of responses per reinforcer and an increase in the number of reinforcers earned. For both ratio and yoked-interval conditions, overall response output was either a monotonically increasing or bitonic (increasing then decreasing) function of unit price. On the whole, results suggest that the downward slope of demand curves was determined primarily by delay to food. Findings are discussed in terms of a unit-price model that includes handling and reinforcer immediacy as additional costs.