Whenever reporting on the cognitive abilities of animals to lay audiences, one is regularly confronted with the question of whether one is suggesting that animals are, in fact, intelligent. This chapter presents an interdisciplinary consensual overview of intelligence as a behavioral disposition displayed by some animals, humans included. Using more scientific methods, scholars have been interested in interspecific differences such as whether dolphins are more cognitively capable than monkeys. However, the design of a universal test of animal intelligence has turned out to be difficult. Humans' singular ability to form multifarious concepts is considered an essential element of our intellectual superiority. In addition to experiments on animal and human intelligence, this chapter also discusses concept formation, mental rotation, transitive responding, and the evolution of intelligence.