Try this: after you've gone through the activity, watch the Koko videos again but this time with the sound off. Without the distraction of the music and narration, your students might find it easier to detect moments when the trainer is modeling and rewarding Koko for her actions.
After participating in the activity, you could have students write an essay on one of the following topics:
Shaping (the process of reinforcing many small behaviors to build up a complex behavior)
Anthropomorphism (our tendency to attribute human emotions to animals and objects)
Confirmation Bias (our tendency to see what we want to see)
Have students go to YouTube and find more videos on Koko:
Find a moment in one of these videos when it appears that Koko is clearly being prompted and rewarded by her trainer to get her to do a sign. Explain what you've found.
Find a moment which you think is very hard to explain given what we've learned about rewards and anthropomorphism - a moment you think Koko is truly communicating. Explain what you've found.
This exercise was made with Google Forms. Here's the link. Feel free to make a copy to your Google account. You can delete the previously collected data and gather your own.