Second-order schedules of token reinforcement with pigeons: Effects of fixed- and variable-ratio exchange schedules

Pigeons' key pecks produced food under second-order schedules of token rein forcement, with light-emitting diodes serving as token reinforcers. In Expe riment 1, tokens were earned according to a fixed-ratio 50 schedule and wer e exchanged for food according to either fixed-ratio or variable-ratio exch ange schedules, with schedule type varied across conditions. In Experiment 2, schedule type was varied within sessions using a multiple schedule. In o ne component, tokens were earned according to a fixed-ratio 50 schedule and exchanged according to a variable-ratio schedule. In tire other component, tokens were earned according to a variable-ratio 50 schedule and exchanged according to a fixed-ratio schedule. In both experiments, the number of re sponses per exchange was varied parametrically across conditions, ranging f rom 50 to 400 responses. Response rates decreased systematically with incre ases in the fixed-ratio exchange schedules, but were much less affected by changes in the variable-ratio exchange schedules. Response rates were consi stently higher under variable-ratio exchange schedules than under comparabl e fixed-ratio exchange schedules, especially at higher exchange ratios. The se response-rate differences were due both to greater pre-ratio pausing and to lower local rates under the fixed-ratio exchange schedules. Local respo nse rates increased with proximity to food under the higher fixed-ratio exc hange schedules, indicative of discriminative control by the tokens.