A progressive-duration schedule of reinforcement

• Rats received food reinforcement for depressing and holding down a response lever.
• Duration requirements increased after each reinforcer delivery.
• Breaking points stabilized when environmental conditions were held constant.
• Behavior was sensitive to both food deprivation and reinforcer quality.

We describe a schedule of reinforcement involving systematic, within-session increases in response-duration requirements. Rats received access to appetitive reinforcers for depressing and holding down a response lever. Duration requirements increased after each reinforcer delivery. Sessions ended when reinforcement criteria were unmet for a period of ten minutes. Breaking points, defined as the terminal duration requirement in effect prior to the end of the session, stabilized when environmental conditions were held constant. Breaking points were sensitive to manipulations of both food deprivation and reinforcer quality. Analogous to progressive-ratio schedules, progressive-duration schedules may provide an assay for measuring the amount of behavior an organism will emit for a given reinforcer under current motivational conditions.