 There is good evidence that the child’s progression along this pathway is related to its development of abilities to respond appropriately to the mental states of others, and to the development of its ability to acquire new vocabulary on the basis of an understanding of what the words used by its mother refer to. A longitudinal study suggests that the earlier stages in this pathway are predictive of the age at which infants reach the later ones – thereby providing some evidence for the hypothesis that this sequence is a causal one – with the mastery at twelve months of pointing as a means to direct the attention of others being predictive of false belief understanding at the age of fifty months, even when factors relating to temperament and language are factored out (Sodian &amp; Kristen-Antonow, 2015). Another source of evidence comes from the fact that the arrested development of these attention-involving abilities is a revealing marker of the impairments suffered by autistic children (Kanner, 1943, Hobson and Hobson, 2011).  Further evidence may also come from the fact that a lack of such abilities is related to limitations in the mental-state attribution abilities of non-human primates, although this last claim is more controversial (Call &amp; Tomasello, 2005).