EXP3422L Lab Journal 4 / Experiment 6 Assignment PDF

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E. Hammock conditioning and learning lab journal 4 assignment for experiment 6...

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Running head: LEVER PRESSING UNDER FIXED RATIO REINFORCEMENT

Experiment 6: Lever Pressing Under Fixed Ratio Reinforcement Name Date Rat ___

LEVER PRESSING UNDER FIXED RATIO REINFORCEMENT 2 Purpose The purpose of this experiment was to continue conditioning a rat’s lever pressing behavior under an intermittent reinforcement schedule. An intermittent reinforcement schedule refers to when a behavior is reinforced only some of the time. The specific type of intermittent reinforcement schedule that was utilized in this experiment is a fixed ratio schedule of reinforcement. Under a fixed ratio schedule, reinforcement is given after a certain number of the target behavior have been elicited. For example, when reinforcement is given after four lever presses, it is referred to as a fixed ratio (FR) 4 schedule of reinforcement. It was hypothesized that by utilizing the process of leaning, a rat’s lever pressing behavior would be shaped to press the lever under an FR5 condition. Leaning refers to the process of reducing the frequency of reinforcement gradually. Procedure Prior to beginning the experiment, a Skinner box was set up according to the instructions found in the Conditioning and Learning Student Lab Manual (p. 63). Following set up, a rat was placed in the Skinner box for a two-minute acclimation period. During the acclimation period, no lights were on and the levers were not active. Following the acclimation period, the right and left levers and lights were activated on an FR1 schedule. One minute of baseline data were collected under this condition. After baseline data were collected, another minute of FR1 data were collected. The Skinner box console was then reset to an FR2 schedule, where left and right lights and levers were both active again. Switching to an FR2 is the first step in leaning toward the goal of getting to FR5. Data were collected under this condition in minute-long intervals until there were five consecutive ratio runs without ratio strain. A ratio run refers to the period of time and

LEVER PRESSING UNDER FIXED RATIO REINFORCEMENT 3 number of behaviors elicited between each reinforcement. A ratio strain is when there is a pause of five seconds or greater between responses within a ratio run, and may indicate that the schedule is being leaned too quickly for the rat. On the other hand, a post reinforcement pause (PRP) is a pause after the required number of lever presses have been elicited and reinforcement has been given. PRP is normal and should not cause concern. After five consecutive ratio runs without a ratio strain, the Skinner box console was reset to an FR3 schedule. Once again, left and right lights and levers were active. Data were collected in minute-long intervals until there were five consecutive ratio runs without ratio strain. The console was then reset to an FR5 schedule, with right and left lights and levers active. Data were collected in minute-long intervals until there were five consecutive ratio runs without ratio strain. After the five consecutive trials, the experiment has been completed. If there are five consecutive ratio runs with ratio strain at any point in the experiment, it is a sign the rat has been leaned too quickly and needs to drop back to the previous schedule of reinforcement. Behavioral Observations During the acclimation period, rat ___ spent her time sniffing around the cage and grooming her front paws. She also attempted to press the levers and sniffed in the dispenser area after each press. Once the light and levers were turned on for baseline data, she began pressing the lever rapidly. Once switched to the FR2 schedule of reinforcement, she immediately pressed the levers multiple times. She had a tendency to complete a few runs without strain, then begin a new run and get distracted by sniffing around the cage or grooming herself. She would then return to lever pressing and finish the strained run then begin a new successful one. She also spent a lot of time throughout the experiment standing in the corner opposite from the levers and sniffing the top of the cage.

LEVER PRESSING UNDER FIXED RATIO REINFORCEMENT 4 When switched to the FR3 schedule, she was initially eliciting a fair amount of lever presses without strain. FR3 is the stage that she began exhibiting PRPs. She regularly alternated lever pressing between the right and left levers, sniffing the place where sugar pellets are dispensed in between. After a lot of initial responses under the FR3 condition, the rat began pressing the levers less. Instead, she began sniffing the top corner opposite from the levers and grooming herself more. Discussion The purpose of this experiment was to continue conditioning a rat’s lever pressing behavior under an intermittent reinforcement schedule. It was hypothesized that by utilizing the process of leaning, a rat’s lever pressing behavior would be shaped to press the lever under an FR5 condition. During the FR1 phase the rat elicited eleven lever presses in two minutes, which averages to 5.5 responses per minute. Under the FR2 condition, she elicited a total of 90 lever presses in eight minutes. This averages to 11.25 lever presses per minute, which is the highest average response rate out of all of the conditions. The FR3 condition lasted 35 minutes, and a total of 126 lever presses were elicited. This averages to 3.6 responses per minute. Criteria for completion under the FR3 schedule was not met, so the experiment never moved on to the FR5 condition. The first ratio strain occurred in the first FR2 trial, which is not representative of all of the data from the experiment. This ratio strain more than likely just occurred because of the change to a new condition, but it is seemed to be a natural response to change when it occurred in small amounts. The rat appeared to catch on quickly and returned to only occasional ratio strains under the FR2 condition. Following the transition to the FR3 condition, ratio strains began to return in larger numbers. Based on observations, the rat’s behavior did not lead to the conclusion that these

LEVER PRESSING UNDER FIXED RATIO REINFORCEMENT 5 strains were because the schedule was leaned too quickly. Her lack of interest in lever pressing behavior under the FR3 condition led to the conclusion that the strains were more likely due to satiation or tiredness. The rat was rewarded with a lot of sugar pellets under the first two conditions, and probably did not feel as strong of a desire to keep exerting herself for the reward. Due to time constraints, it was decided that taking the rat out for a rest-period and dropping back to the FR2 condition was not feasible. The hypothesis was not supported, but the experiment was still successful. With more time, the experiment could be done more correctly and the results would likely support the hypothesis....