RATE OF A MAINTAINED OPERANT AS A FUNCTION OF TEMPORAL POSITION WITHIN A SESSION

McSweeney and her colleagues (e.g., McSweeney, Hatfield, & Allen, 1990 ) have demonstrated reliable, large magnitude rate changes in maintain ed operants within daily sessions under a wide variety of reinforcemen t schedules. The present paper examined the role of schedule of reinfo rcement, reinforcement rate, and total amount of food access in determ ining those within-session rate changes. When median rates across bird s were considered, all procedures resulted in a brief period of an inc reasing rate, followed by a modest rate loss across the major portion of the session. However, not all individuals exhibited that pattern. W hen the amount of food access per session was limited by lower reinfor cement rates, shorter sessions, or shorter reinforcement durations, th e magnitude of the within-session rate change was reduced from that oc curring without those constraints. Additionally, under the conditions that produced strong within-session rate changes, the magnitude of the within-session rate loss was correlated with the bird's body weight. These effects are consistent with what is typically labeled satiation.