Training Session Two: Shaping Tessa

Goal
To shape Tessa the Rat until she forms an observable association between the act of pressing the bar in the Operant Box and the receipt of reinforcement in the food magazine. Shaping is the process of reinforcing successive approximations of the desired behavior until the organism is performing the desired response. 

Procedure
Food deprivation was continued to encourage Tessa to seek reinforcement in the Operant Box. At the time of training, Tessa weighed approximately 205 grams which was over her target weight of 202 grams. Training began at 3:00 PM in Operant Box 3 of the Learning Laboratory. Successive approximations of bar-pressing behavior were reinforced. First, Tessa was reinforced for turning or showing interest in the bar. Next, she was reinforced for moving towards the bar. Rearing behaviors were reinforced near the bar, and touching the bar was instantly reinforced. Variants of behavior resembling the target, but not leading to proper shaping, were not reinforced. For example, rearing behavior away from the bar were not reinforced; likewise, interest in the underside of the bar was not reinforced. The training session continued for 21:59, consisting of 134 manual reinforcements and 59 bar-presses.

Results
Tessa developed a strong association between the action of bar-pressing and the receipt of reinforcement. She was reinforced for multiple behaviors, but the final half of the training session was focused only on bar-pressing behaviors. Tessa responded to these reinforcements, and she was able to maintain steady bar-pressing behavior for nearly four minutes (see graph below).

Cumulative Record for Shaping

Discussion
Tessa's various forms of behavior have both positive and negative effects on the process of shaping. Because she produced a wide array of behaviors, it was not difficult to begin reinforcing the behaviors which resembled bar-pressing. However, once she developed an understanding of the contingency between bar-pressing and reinforcement, she continued to display a wide variety of other behaviors. These include rearing behaviors throughout the cage, interest in the lights above the food magazine and bar, and interest in the front of the cage and floor of the cage. Tessa received manual reinforcement when she lingered too long on one side of the cage. Rearing behaviors were reinforced after Tessa returned to bar level; thus, she was reinforced to stay at the bottom of the box instead of rearing or jumping towards the top. These reinforcements encouraged Tessa to return to the food magazine, which reminded her to engage in the bar-pressing activity.

Training day 2 began at 3:00 PM on September 21st, 2012.