title: Aspartame demand in rhesus monkeys: effects of volume and concentration manipulations.
abstract: Three rhesus monkeys' lever presses produced aspartame-sweetened water according to a fixed-ratio schedule. The response requirement was increased across sessions and a demand-function analysis was used to assess the reinforcing effectiveness of different magnitudes of aspartame by manipulating reinforcer duration (1 and 3s) in Phase 1 and concentration (0.3, 0.5, 0.7, and 1.0mg/ml) in Phase 2. When duration was manipulated, the number of aspartame deliveries was mainly a function of the response requirement rather than unit price (responses/duration), suggesting that changes in duration did not significantly affect the reinforcing effectiveness of aspartame. When concentration was manipulated and the lowest concentration excluded, consumption was best described by unit price (responses/concentration) in two monkeys and by the response requirement in the third. Although results from the concentration manipulation provide some evidence that consumption was modulated by unit price, the results overall suggest that scalar equivalence does not exist between the components of unit price; specifically, the response requirement exerted a larger influence than duration or concentration on total consumption. Finally, a normalized demand analysis revealed that aspartame is a more elastic commodity than food and drug reinforcers.
authors.affiliation: Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA. twadegal@umich.edu
authors.forename: Tammy
authors.initials: T
authors.lastname: Wade-Galuska
authors.forename: Chad M
authors.initials: CM
authors.lastname: Galuska
authors.forename: Gail
authors.initials: G
authors.lastname: Winger
authors.forename: James H
authors.initials: JH
authors.lastname: Woods
mesh_terms: D000818:Animals; D001218:Aspartame / Q000008:administration & dosage / Q000494:pharmacology*; D001522:Behavior, Animal; D002755:Choice Behavior; D004327:Drinking Behavior; D004334:Drug Administration Schedule; D005260:Female; D008253:Macaca mulatta; D009994:Osmolar Concentration; D012054:Reinforcement, Psychology; D013549:Sweetening Agents / Q000008:administration & dosage / Q000494:pharmacology*; D014867:Water
chemical_list: D013549:Sweetening Agents; D014867:Water; D001218:Aspartame