Hello,
You have done a really great job with this topic! Some things I would add or change are: I would add a sentence or two at the end of the lead section mentioning who the key people are and what the key model organisms are that you will be looking at later. That way if someone comes to this page and wants to know what role a specific person played to comparative cognition they are scroll right down to that person knowing that they will be there. When you get to the model organisms section I would include which of the key people used which model organisms when applicable. In the model organisms section, I would suggest bolding the names of the people you mention or any key terms (such as puzzle-box), that way it draws the reader's attention, and by just simply skimming the article people can determine what is an important method used with that model organism. If it is possible I would add more to the section on felines (but only if you can find more relevant information). That section just seems smaller in comparison to the other sections you have. You did a really great job maintaining a neutral tone throughout. I'm not sure if its just because it is in a sandbox or not but it appears as though your referances are listed twice. Once in a referance section and once in an external links section. I do not think that you need both if they are the same.
You did a really great job with your article. You really know your topic well and did a wonderful job explaining it.