As soon as I put Li'l Swanson in the operant box, she went straight to the bar and placed her paws on it, then looked for a reward. I rewarded her the first few times that she placed her paws on the bar, but after the first few minutes I switched to only rewarding her every 3 or 4 times she placed her paws on the bar in the hopes that she would get frustrated and press harder on the bar, my ultimate goal. She started pressing on the bar after she'd been in the box for about 8 minutes, and by the end of the 30 minutes session she was pressing the bar consistently--she had been shaped! Overall, the shaping process went as I expected, based on our class readings. By using "successive approximations" of the desired behavior, I trained Li'l Swanson to press the bar--trying to get her to press the bar from the get-go would have been nearly impossible, but by rewarding behavior in small steps, I was able to accomplish my task.
In the graph above, the x-axis represents time passed, and the y-axis represents lever presses. As you can see, at the beginning of this session with Li'l Swanson, she did not press the bar very often. However, as time went on, her bar presses increased greatly--by the end of the shaping session, she pressed the bar about 67 times.
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