The effect of geometric and arithmetic progressions on demand for food under concurrent progressive-ratio and fixed-ratio schedules

The aim of this study was to compare performance of 12 possums under concurrent progressive-ratio and fixed‐ratio schedules to investigate whether using different schedule and progression types would affect the determination of relative food preference. A progressive-ratio schedule was increased within (PR FR) or across sessions (PFR FR) and the alternative schedule remained constant. The progression of the incrementing schedule was also varied between a geometric sequence (basis 2), and an arithmetic sequence (step 5). The food pairs of berries and egg, and a barley mix and oats were tested. The parameters of the exponential (Hursh & Silberberg, 2008) and cross‐price demand (Hursh, Madden, Spiga, DeLeon, & Francisco, 2013) models predicted estimates that differed in their description of demand across schedules, progression and food type. Cross points were the most stable measure and showed that when preferred foods were available under the incrementing schedule higher cross points were observed.