Cognitive science studies behavior, but in a different way than psychology. For most psychologists, behavior is the object of study, but for cognitive scientists, behavior is a dependent variable of cognition. For cognitive science, cognition, not behavior, is the object of study. Cognition exists in humans, animals, and in machines. In humans and animals, cognition evolved, whereas in machines it is created by humans. A good example of the difference between evolved and created cognition is how humans and computers each play chess. Chess is a human game, but now computer programs can also play. Once a year, the best programs play each other, and then, the winner plays a human grand master player. To date, the human has always won, soon, however, computers will probably win. Computers use their huge memories to look many moves ahead. Humans play in a completely different way, looking ahead only a move or two, while analyzing the current board patterns. Both computers and humans, however, adjust their behavior to cope with the "cognitive" and environmental stimuli presented by the game of chess.
So, anything that thinks in any way could be a subject for a cognitive scientist. However, the behavior of the thinking object will not be the point of study; rather, the point of study will be the mechanisms that lead to the subject's behavior. That difference in emphasis, toward cognition and using behavior as a clue for that cognition, is what differentiates cognitive science, strictly defined, from psychology. However, cognitive science is an inclusive term and many psychologists would consider themselves cognitive scientists without adopting the definition of cognitive science given above.