Constraints on the lexicons of human languages have cognitive roots present in baboons (Papio papio).

Using a pattern extraction task, we show that baboons, like humans, have a learning bias that helps them discover connected patterns more easily than disconnected ones-i.e., they favor rules like "contains between 40% and 80% red" over rules like "contains around 30% red or 100% red." The task was made as similar as possible to a task previously run on humans, which was argued to reveal a bias that is responsible for shaping the lexicons of human languages, both content words (nouns and adjectives) and logical words (quantifiers). The current baboon result thus suggests that the cognitive roots responsible for regularities across the content and logical lexicons of human languages are present in a similar form in other species.