CONCURRENT RATIO SCHEDULES: FIXED vs. VARIABLE RESPONSE REQUIREMENTS¹

Abstract

Rats were trained on concurrent fixed-ratio variable-ratio or concurrent fixed-ratio mixed-ratio schedules of food reinforcement. The variable-ratio schedule was composed of an arithmetic sequence of 11 ratios that averaged 50; the mixed-ratio schedule consisted of equiprobable ratios of 1 and 99. Fixed-ratio values, varied over experimental conditions, included 25, 35, 50, 60, and 99. The proportion of responses and time allocated to the variable- or mixed-ratio schedule increased as the size of the fixed ratio increased. For most subjects, higher proportions of responses and time were maintained on the fixed-ratio schedule at fixed-ratio values of 25 and 35; higher proportions of responses and time were maintained on the variable- or mixed-ratio schedule at fixed-ratio values of 50 or higher. On concurrent variable-ratio fixed-ratio schedules, the tendency for responding to be maintained exclusively by one schedule was related to the difference in local reinforcement rates obtained from those schedules. Exclusive responding was approximated when the difference in local reinforcement rates obtained from those schedules was large; responding was more evenly distributed between the schedules as the difference in the rates at which reinforcement was obtained from each decreased.

Herrnstein’s equation for the rates of responding during concurrent schedules

“…Second, Ro did not differ systematically for some differences in component schedules. There were no consistent differences in the size of R o between FR and VR or MR components (Rider, 1979), or between FI and VR components (Rider, 1981). Third, R, did not usually vary with the operanda used in the components.…”

“…The two studies that used two different operanda (Davison & Ferguson, 1978;McSweeney, 1978) and the two studies that used different reinforcers in the two components (Hollard & Davison, 1971;Matthews & Temple, 1979) fell into the intermediate or poor category. All studies that used two different simple schedules also fell into the intermediate or poor category (Herrnstein & Heyman, 1979;LaBounty & Reynolds, 1973;Nevin, 1971;Rider, 1979Rider, , 1981Trevett et al, 1972), except Lobb and Davison (1975). The results of Lobb and Davison's study fell into the best category, but were on the borderline.…”

“…Second, k varied with the simple schedule used in the components. The value of k was usually larger for fixed-ratio (FR) than for VR or mixedratio (MR) components (Rider, 1979), for VR than for VI components (Rider, 1981), and for FI than for FR components (LaBounty & Reynolds, 1973).…”

Stimulus contingency and the malleability of species‐typical auditory preferences in Northern bobwhite (Colinus virginianus) hatchlings

“…The observation that variable schedules produces higher and more steady levels of responding than fixed schedules has been long established in the learning literature (e.g., Ferster & Skinner, 1957). It is also well established that given a choice between a variable and FR schedule, a variety of species will prefer the VR over the FR schedule (e.g., Fantino, 1967; Field, Tonneau, Ahearn, & Hineline, 1996; Rider, 1979; Sherman & Thomas, 1968), even when this schedule provides fewer reinforcers or less stimulation (e.g., Ahearn, Hineline, & David, 1992). Such a preference for variability implies an affective and/or motivational response to stimuli encountered or delivered with a higher degree of variability that could facilitate learning and memory.…”

The effect of rate of reinforcement and time in session on preference for variability

“…Differences in habituation should be stronger later in the session than earlier, because these differences should accumulate with successive rein- Autor, 1969;Bateson & Kacelnik, 1995;Case, Nichols, & Fantino, 1995;Davison, 1969Davison, , 1972Frankel & vom Saal, 1976;Herrnstein, 1964;Hursh & Fantino, 1973;Killeen, 1968;Lobb & Davison, 1975;Navarick & Fantino, 1972Trevett, Davison, & Williams, 1972 Mixed (MR) or Variable (VR) Ratio Schedules Are Preferred to Equally Rich Fixed Ratio (FR) Schedules Ahearn, Hineline, & David, 1992;Fantino, 1967;Mazur, 1986;Morris, 1986;Navarick & Fantino, 1972;Rider, 1979, 1983a(note that Rider, 1983a, includes information on both sides of this issue); Sherman & Thomas, 1968 More Variable VR Schedules Are Preferred to Less Variable VR Schedules Ha, 1991;Ha, Lehner, & Farley, 1990 VI Schedules Are Preferred to Equally Rich FR Schedules Bacotti, 1977 VR Schedules Are Preferred to Equally Rich FI Schedules Rider, 1981 Variable Times From the Start of a Trial Are Preferred to Fixed Times Logan, 1965;Reboreda & Kacelnik, 1991 Variable or Mixed Delays From a Response to a Reinforcer Are Preferred to Fixed Delays Bateson & Kacelnik, 1997;Cicerone, 1976;Mazur, 1984Mazur, , 1986Pubols, 1962;Rider, 1983b;Zabludoff, Wecker, & Caraco, 1988 forcer presentations. Habituation theory predicts that preference for variability should be strongest when differences in habituation are strongest.…”