Recent studies reveal spontaneous implicit false-belief understanding in infancy. But is this early ability genuine theory-of-mind? Spontaneous tasks may allow early success by eliminating the selection-response bias thought to underlie later failure on standard tasks. However, using anticipatory eye gaze, we find the same bias in non-verbal tasks in both preschoolers and adults. We argue that the bias arises from theory-of-mind competence itself and takes the form of a rational prior to attribute one's own belief to others. Our discussion then (...) draws attention to a number of other inferential hallmarks of early belief-desire reasoning that together suggest it is the real deal. (shrink)