To what extent do children with autism (AD) versus typically developing children (TD) rely on attentional and intentional cues to learn words? Four experiments compared 17 AD children (M age 5 5.08 years) with 17 language-and 17 mental-age-matched TD children (M ages 5 2.57 and 3.12 years, respectively) on nonverbal enactment and word-learning tasks. Results revealed variability in all groups, but particularly within the AD group. Performance on intention tasks was the most powerful predictor of vocabulary in the AD group but not in the TD groups. These findings suggest that word learning cannot be explained exclusively by either attentional or intentional processes, and they provide evidence of a special role for intentional understanding in the vocabulary development of AD children.Children acquire vocabulary at an impressive pace (Carey, 1978), and they acquire it primarily in the context of social interaction with other human beings (Hoff, 2003;Hoff & Tian, 2005;Opie, Steele, & Ward, 2004;Rowe, 2004;Tomasello, 1999; but see Chen & Peng, 1995). Hotly debated, however, is the exact function that social interaction plays for children learning to map words onto referents. Does social interaction offer perceptual cues that direct attention to word referents? Or does it provide a gateway to a speaker's communicative intent, thus focusing listeners on the object or action that the speaker had in mind? Might there be a developmental progression with children first attending to the perceptual, attentional elements of social interaction and only later to the intentional cues to word reference? It has been difficult to distinguish empirically among these accounts. A comparison of the way typically developing (TD) and autistic (AD) children learn words offers a window onto the role that social information plays in word learning. It has been argued that AD children pay less attention to social intentional cues than do TD children (Baron-Cohen, 1995). If true, and AD children nonetheless learn words in a manner similar to TD children, then understanding social intent might not be necessary for word learning. Furthermore, as AD children are somewhat heterogenous in their ability to access intentional cues, studying them offers a second way to examine the relative import of attentional and intentional social cues in vocabulary acquisition.There are a plethora of theories that have been developed to account for patterns of early word learning. For example, there is the view that children's word learning is guided by a set of constraints that limit the number of hypotheses children need to make for what a word might mean (Booth, Waxman, & Huang, 2005;Cimpian & Markman, 2005;Merriman & Evey, 2005). For the present purposes, however, we will consider only three types of theories: attentional, intentional, and hybrid. Attentional theories hold that social exchanges replete with movement, object handling, and gestures highlight certain objects and actions in the environment over others. Hearing a word in the presence of an inter...