Hello @aghunter :) What a beautiful comment this is.
I really appreciate your honesty as a parent. I am not a parent; but I have a beautiful little niece and a very naughty little nephew. I couldn't stop thinking of them while watching Theroux's documentary. As you can see in my post, similarly to you, the question that permeates my mind is whether a child that young is capable of making such a decision!
I am also fascinated by primates and am particularly interested in their general behaviour and cognitive capacities. Like you said, certain traits were more evident in certain species than in others, like for example boy chimpanzees (male dominated and violent) are the ones, across the species mentioned here, more likely to explore new grounds further from their mothers and develop riskier behaviours; while the Capuchin females even have more of a fruit rich diet, which contribute to a more calmer environment.
Still, despite their different traits similar behaviour was seen in the boys and girls across the species mentioned here :) Here is the link to a piece of research that explores the behaviours of a variety of species http://onlinelibrary.wiley.com/doi/10.1002/jnr.23862/full; you will most likely find there the controls you are interested in! I hope it can contribute to your next project!
All the best to you and your family :))