Shared intentionality theory posits that at age 3, children expand their conception of plural agency to include 3- or more-person groups. We sought to determine whether this conceptual shift is detectable in children's pronoun use. We report the results of a series of Bayesian hierarchical generative models fitted to 479 English-speaking…

We compared the performance of 3- and 5-year-old children with that of chimpanzees in two tasks requiring collaboration via complementary roles. In both tasks, children and chimpanzees were able to coordinate two complementary roles with peers and solve the problem cooperatively. This is the first experimental demonstration of the coordination of…

There is currently much controversy about which, if any, mental states chimpanzees and other nonhuman primates understand. In the current two studies we tested both chimpanzees' and human children's understanding of both knowledge-ignorance and false belief--in the same experimental paradigm involving competition with a conspecific. We found that…

It has been repeatedly shown that when asked to identify a protagonist's false belief on the basis of his false statement, English-speaking 3-year-olds dismiss the statement and fail to attribute to him a false belief. In the present studies, we tested 3-year-old Japanese children in a similar task, using false statements accompanied by…

Compared performance of preschool children, chimpanzees, and orangutans on nonverbal task of false-belief understanding and tested children's performance on a verbal version of the same task. Found that children's performance on verbal and nonverbal tasks were highly correlated, and no chimp or orangutan succeeded in the nonverbal false-belief…

This article reports 2 experiments examining the changing role of iconicity in symbol learning and its implications regarding the mechanisms supporting symbol-to-referent mapping. Experiment 1 compared 18- and 26-month-olds' mapping of iconic gestures (e.g., hopping gesture for a rabbit) vs. arbitrary gestures (e.g., dropping motion for a rabbit).…

Compared comprehension of novel communicative signs to assist 2.5- and 3-year-old humans, chimpanzees, and orangutans find hidden objects during a hiding-finding game. Found that children at both ages performed above chance with all signs. No ape performed above chance for any signs not known before the experiment despite three times as many…