Patterns of Responding Within Sessions

Abstract

Rates of responding changed systematically across sessions for rats pressing levers and keys and for pigeons pressing treadles and pecking keys. A bitonic function in which response rates increased and then decreased across sessions was the most common finding, although an increase in responding also occurred alone. The change in response rate was usually large. The function relating responding to time in session had the following general characteristics: It appeared early in training, and further experience moved and reduced its peak; it was flatter for longer sessions; and it was flatter, more symmetrical, and peaked later for lower than for higher rates of reinforcement. Factors related to reinforcement exerted more control over the location of the peak rate of responding and the steepness of the decline in response rates than did factors related to responding. These within-session changes in response rates have fundamental theoretical and methodological implications.

Prospective factors contribute little to within-session changes in responding

“…Fifteen sessions were conducted instead of 30 for the predictable conditions, to try to ensure that all subjects lived long enough to complete the experiment. Past results had indicated that within session changes should occur when 15 sessions were conducted (e.g., McSweeney & Hinson, 1992). Figure 1 presents the rates of responding (responses per minute) as a function of successive components for each unpredictable session duration.…”

“…To put this in perspective, Catania and Reynolds (1968, Experiment 1) varied the programmed rate of reinforcement from 8.4 to 300 reinforcers per hour and observed only approximately a doubling of response rate. Second, within-session changes may be highly orderly, occurring for individual subjects responding in individual sessions (e.g., McSweeney & Hinson, 1992 throughout the session, not just at the beginning (e.g., McSweeney et al, 1990). Third, within-session changes occur quite generally.…”

Within-Session Changes in Response Rate: Implications for Behavioral Pharmacology

“…Within-session changes in responding are large, orderly, and reliable (e.g., McSweeney & Hinson, 1992). They occur for a wide variety of species, responses, and reinforcers (e.g., McSweeney & Roll, 1993).…”

“…Rate either increases early in the session and remains stable for the remainder of the session (McSweeney, Roll , & Cannon, 1994), decreases throughout the session (McSweeney & Roll , 1993), or increases and then decreases during a session (McSweeney & Hinson, 1992). An examination of the literature on drug self-administration reveals the same three patterns of responding.…”

Within-session changes in responding during concurrent schedules that employ two different operanda

“…The recent discovery of systematic changes in responding within sessions may cause problems for this quantification (McSweeney, Hatfield, & Allen, 1990). Within-session changes in responding can be large and they occur for many species performing a variety of responses under many different conditions (MeSweeney & Roll, 1993), including concurrent schedules (McSweeney & Hinson, 1992).…”