Lab Report Results Section

Apparatus

A standard modular test chamber – Med Associates, Model Number ENV-008 – was used to conduct the experiment in a lab classroom of about 24 students and 11 other experimental stations. The chamber, located in a sound-attenuating enclosure with a window on the front, measured 21” long, 13.75 inches wide, and .5 inches high. The ventilation fan in the enclosure of the chamber was used to minimize noise outside the chamber. Outside the chamber (and behind the wall with the lever) was a feeder (2 cm from the floor) that contained 45-mg BioServ grain pellets that were delivered (into receptacle 5.1 cm long and wide). The interior of the chamber was 30.5 cm long, 24.1 cm wide, and 21 cm high. Two 4.8 by 1.9 cm high levers stood 7 cm from the floor and 1 cm from the wall of the chamber. Above the levers was a 2.5 cm diameter light. Centered on the wall opposite of the levers, stood a houselight with a 100-mA bulb, that was 1 cm from the ceiling of the chamber. t. We used a Microsoft computer with corresponding computer programs to control the sessions and record data at the end of each session.

Procedure

Habituation. The procedure consisted of sessions that were ran 5 days a week around the same time. The initial training consisted of 4 sessions of habituation. During the habituation training, the houselight of the chamber was on. We differentially reinforced successive approximations of lever pressing by initiating a pellet when the rat performed a habitual behavior such as; grooming, sniffing the ceiling, and/or climbing the wall of the chamber. Each time the rat performed each of the behaviors, a lever extended into the chamber and we delivered pellets by stimulating a response. If the rat pressed the lever on its own, then the lever retracted, and pellets were delivered automatically. Each session was recorded in 5-min blocks. The lever pressing was successfully shaped after the rat made at least 3 lever presses on its own. Once the rat began pressing the lever on its own without an initial stimulus, we stopped delivering the pellets.

Pellet training. After lever shaping was complete, the conditions were contingent on a fixed-ratio (FR) schedule using the left and right lever in the chamber. The light in the chamber shined as each lever was extended and turned off when the lever retracted. The number of pellets that were delivered during the next 3 sessions ranged from 45-50 pellets. With each reinforcement of a pellet, the sound of the dispenser and light of the chamber flashed. The goal was to shape the rat to respond to the stimuli – the light and the sound of the feeder – signaling the delivery of a pellet. Each pellet-training session lasted between 15-20 min. Once the rat adapted to the stimuli of the receptacle within a 1-s pause after the delivery of the pellet, we concluded the pellet training and changed the condition of the reinforcement.

Shaping. After the end of the FR 1 training, multiple FR FR schedule resulted in both left and right levers retracting one at a time. The houselight and the lights of the chamber remained on and with each lever retraction, the lever lights came on. The reinforcement was only 1 pellet at time. During this session, there were 41 total pellets that were delivered – 21 from the right and 20 from the left (or 21 from the left and 20 from the right). After each retraction from the levers, there was approximately 2-s pauses after the delivery of a pellet before the other lever was retracted. The condition of the schedule was then manipulated, and we began delivering up to 50 pellets. We began spacing the pellet deliveries apart by longer durations once the rat got accustomed to the reinforcement. While running on schedules in 5 sessions MULT FI conditions, the schedules were manipulated and the retraction of the unfavorable lever was increased by 5 s., while the favorable lever remined constant at FI 10. We began initiating the first lever and pellet delivery after 5-10 s then 20-30 s. The session concluded after all 50 pellets were delivered. Comment by Hughes, Christine: Reinforcer is always 1 pellet

Multiple FI FI schedule. Sessions were divided into four different conditions: Unfavorable-unfavorable, unfavorable-favorable, favorable-unfavorable, and favorable-favorable. The first multiple FI 5-10 FI 10-s schedule lasted after 5 sessions, with each session lasting about 20-min. After the initial multiple FI 10 schedule, we changed the transitions to Left-favorable FI 10 FI 15-s schedules. We ran 7 sessions under this schedule for approximately 20 min. After 40 pellets were delivered during this schedule, we ran the rat on a FI 10 FI 25 s schedule for 8 different sessions. We then manipulated the transitions by running the four different conditions on a FI 10 FI 30 schedule for 8 sessions that lasted for approximately 25 min. After running on the FI 10 FI 25 schedule, we ran all four conditions on a FI 10, FI 20 s schedule for 8 sessions. After the eight session of the Left favorable FI 10 FI 20 schedule, we concluded the experiment and recorded the data for all sessions after each condition.

Data Analysis

Results

Figure one shows an increase in PRP as the transition from unfavorable to favorable on a FI 10 FI 10 schedule. The mean pause in the FI 10 were slighter smaller than the mean pauses for the FI 10 FI 15 condition (about 3 times the rate). In the FI 10 FI schedule, the PRP was shorter during the longer UF-F condition than the F-UF favorable condition. Lever switching began in the FI 10 FI 15 condition. A

Discussion

In the FI 10 FI schedule, the PRP was shorter during the UF-F condition than the F-UF favorable condition. The change across these conditions could have resulted from the difference in the number of sessions between the two. In the FI 10 FI schedule, there were only 5 sessions with these transitions. After the FI 10 sessions, the conditions were manipulated to a FI 10 FI 15 during 8 sessions,

References

Harris, A., Foster, T., Levine, J., & Temple, W. (2012). Effects of a signaled delay to reinforcement in the previous and upcoming ratios on between-ratio pausing in fixed-ratio schedules.

Lowe et al., 1983. The role of verbal behavior in human learning: infant performance on fixed- interval schedules. Journal of the experimental analysis of behavior, 39, 157-164

Mazur, J. 1983. Steady-state performance on fixed-, mixed-, and random-ratio schedules. Journal of the experimental analysis of behavior, 39. 293-307.

Perone, M., Courtney, K., 1992. Fixed-ratio pausing: joint effects of past reinforcer magnitude and stimuli correlated with upcoming magnitude. J. Exp. Anal. Behav. 57, 33–46.