I think that's the psychology of it: https://www.youtube.com/watch?v=-KSryJXDpZo https://www.youtube.com/watch?v=-KSryJXDpZo (video of monkey getting a grape a

I think that's the psychology of it: https://www.youtube.com/watch?v=-KSryJXDpZo https://www.youtube.com/watch?v=-KSryJXDpZo (video of monkey getting a grape and the other monkey getting a cucumber)