Part 2: Training Sniffy the Virtual Rat Fixed Interval & Extinction

 Goal 3: Fixed interval schedule was put on Sniffy after magazine training and shaping were completed. Reinforcement delivered after a set amount of time passes. 

Procedure: In this schedule, Sniffy was given reinforcement after 15 second intervals (FI-15). Sniffy pressing the level were more far out in this schedule compared to the CRF (continuous reinforcement). Time was sped up and data was recorded in the cumulative recorder.

Results/ Discussion: Instead of rewarding Sniffy every time he pressed the lever/bar, Sniffy was rewarded after a set time. Sniffy got kind of confused when he pressed the lever and no food came out. He started pressing the bar fast and several times in a row. Before this schedule, Sniffy in shaping pressed the lever in a methodical manner, however in fixed interval he was pressing the bar more aggressively. After 5-10 minutes, Sniffy figured out he would have to wait longer to get a pellet. The cumulative recorder, evidenced in figure 3 below, shows that Sniffy started to receive a pellet of food after waiting 15 seconds.  Under fixed interval, the performance is not steady like under fixed ratio schedule. Sniffy increased the rate of pressing the lever when he closer to the end of the interval. Overall, what I learned about fixed interval schedule is behavior is reinforced the first time it occurs after an interval.

Figure 3: Cumulative Recorder for Fixed Interval (FI) Reinforcement (sloped lines with dashes represent when Sniffy presses the bar-presses.FI-15 indicated the start of fixed interval reinforcement for 15 seconds.

Goal #4: Perform extinction on Sniffy’s previously trained fixed interval behavior. Extinction is when the conditioned behavior eventually stops. 

Procedure: Extinction is a very simple concept. I set the program to extinct Sniffy’s previous fixed interval (FI-15) behavior. I sped up the process and watched as Sniffy’s behavior went away.

Results/Discussion: At first, Sniffy pressed the bar a lot at the beginning of extinction. However, over time he realized no matter how many times he pressed the lever or waited, no reinforcement would be delivered. When Sniffy no longer pressed the lever, also known as loss of instrumental response, extinction was complete/ reached. One observation I noticed was that there was a lot of variability in Sniffy's behavior due to extinction. I'm also sure there was also some level of aggression because extinction does cause a spike in emotional behavior. For example, Sniffy wandered to different parts of the operant box.  This claim can be seen in figure 4 below. Sniffy’s response rate dropped drastically at the end of extinction, the flat line at the bottom of the figure.  

Figure 4: Cumulative Recorder for Extinction.