Three questions were asked that explored the linguistic fine-tuning hypothesis and how parents might model language: (i) do parents significantly tune to their children's productive language or non-verbal cognition during play? (ii) is the level of the linguistic tuning different in the Down syndrome (DS) population compared to a typically developing (TD)-match group population? and (iii) do the two populations differ in requests for labels and the scaffolding responses to the requests? In an exploratory play condition, parents of children with DS used a mean length of utterance (MLU) significantly higher than the MLU used by the parents of younger TD children who were matched for MLU. Thus, the DS parents have a higher baseline MLU, but the non-significant correlations in the DS group do not support parental MLU tuning. There was evidence, however, for parental tuning to the children's lexicon using a number of different words when the DS children were at lower and average levels of receptive syntax and non-verbal cognition. In addition, DS and TD parents requested labels for novel toys with the same frequency, perhaps indicting that all groups of parents are still probing and building their children's lexicons. This is an important finding because it may help to explain why adolescents and young adults with DS have vocabulary comprehension skills greater than one would predict from measures of their production and non-verbal cognition.