After more than two decades of studying the behavior of chimpanzees three themes stand out to me. First, chimpanzees show greater flexibility in their behavior than do monkeys in areas such as information-seeking, confidence monitoring, self-control, and planning for the future. Second, chimpanzees show successes and failures that match human successes and failures of perception and cognition, but chimpanzees also sometimes fail where humans succeed. Third, these successes and failures in cognition in our closest living relatives are fascinating for what they tell us about chimpanzees, about the evolution of cognition, and about the nature of being human. I will highlight studies I have conducted with colleagues that compare chimpanzees, monkeys, and in some cases human children or adults, and I will discuss in detail those which have best demonstrated these three themes.