I have never seen a study showing this. Where did you get this data from? You can make nonhuman mammals follow their instincts all day, but we can't extract much value from that. You can't make them do arbitrary tasks that are physically and mentally within their means all day. You can train animals to do a task once easily, but you can't train it to continue doing said task for the entire day so it can get fed by the end of the day.