An economic analysis of "demand" for food in baboons.
Demand curves from micro-economics map neatly onto FR food schedules with baboons.
01Research in Context
What this study did
The team worked with baboons in a closed economy. The animals lived in cages where every food pellet cost lever presses.
They raised the price step by step. Each new step used a higher fixed-ratio schedule. They tracked how much the baboons ate and how hard they worked.
The goal was to draw a demand curve. The curve shows how intake drops as the response cost grows.
What they found
Food intake stayed high while the price was low. Once the ratio got heavy, intake finally fell.
At the break point, the baboons were eating only 15 to 55 percent of their free-feeding amount. The curve had the bowed shape Hursh’s equation predicts.
How this fits with other research
Saunders et al. (1988) did the first cost-benefit map. They showed that one number—unit price—can collapse many schedules into one curve. Foltin (1991) applies that same ruler to baboons and gets the same bend.
Edwards et al. (1970) poured free extra food into the cage. Response rates barely budged. Together the two papers show that FR performance is sturdy against free food yet fragile against high price.
Howard et al. (1988) added shock risk instead of lever presses. The animals still shifted to fewer, larger meals. All three studies agree: when feeding gets costly, mammals defend calories by changing how often and how much they eat.
Why it matters
You can treat reinforcer cost like price. Plot how many tokens, responses, or minutes your client must pay. If the cost climbs and the behavior holds, demand is inelastic—keep thinning. If intake collapses, you hit the elastic zone—ease up or boost the payoff. The curve gives you an objective place to stop.
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02At a glance
03Original abstract
Responding of 6 adult male baboons (Papio c. anubis) was maintained under a fixed-ratio schedule of food reinforcement during daily 22-hr experimental sessions. Completion of the ratio requirement resulted in the delivery of a single 1-g food pellet; supplemental feeding was limited to a daily fruit ration. Ratio values were increased on Mondays, Wednesdays, and Fridays according to the following schedule: 2, 4, 8, 16, 32, 64, 96, 128. Responding under each ratio value was examined four times. Under the Fixed-Ratio 2 conditions, food intake ranged between 300 and 600 g. Ratios were increased for each baboon until food intake decreased to about 100 g (20% to 30% of Fixed-Ratio 2 intake). Increasing the response cost increased total time responding and total daily responding in all baboons, but this increase in responding was not sufficient to maintain stable food intake. Baboons responded between 90 and 180 min per day. The highest running response rates were observed under the Fixed-Ratio 2 and Fixed-Ratio 4 schedules. Running rate was similar across the larger ratio values (greater than Fixed-Ratio 8) but was lower than that observed under the Fixed-Ratio 2 and Fixed-Ratio 4 schedules. Similar results were observed the four times that each fixed-ratio value was tested. Intake as a function of cost was analyzed by fitting data to the nonlinear equation proposed by Hursh, Raslear, Shurtleff, Bauman, and Simmons (1988) for "demand" functions. Demand for food was inelastic over most of the ratio values until food intake decreased to 15% to 55% of baseline. The results indicate that demand functions are appropriate for the study of food intake in baboons, but also caution that intake at the cost when demand shifts from inelastic to elastic and its relationship to maximal intake should also be included in analyses of demand for a commodity.
Journal of the experimental analysis of behavior, 1991 · doi:10.1901/jeab.1991.56-445