This paper reviews a recent set of behavioural studies that examine the scope and nature of the representational system underlying theory–of–mind development. Studies with typically developing infants, adults and children with autism all converge on the claim that there is a specialized input system that uses not only morphological cues, but also behavioural cues to categorize novel objects as agents. Evidence is reviewed in which 12– to 15–month–old infants treat certain non–human objects as if they have perceptual/attentional abilities, communicative abilities and goal–directed behaviour. They will follow the attentional orientation of an amorphously shaped novel object if it interacts contingently with them or with another person. They also seem to use a novel object's environmentally directed behaviour to determine its perceptual/attentional orientation and object–oriented goals. Results from adults and children with autism are strikingly similar, despite adults' contradictory beliefs about the objects in question and the failure of children with autism to ultimately develop more advanced theory–of–mind reasoning. The implications for a general theory–of–mind development are discussed.