What is 'word understanding' for the parent of a one-year-old? Matching the difficulty of a lexical comprehension task to parental CDI report

Is parental report of comprehension valid for individual words? If so, how well must an infant know a word before their parents will report it as 'understood'? We report an experiment in which parental report predicts infant performance in a referent identification task at 1; 6. Unlike in previous research of this kind (i.e. Houston-Price, Mather & Sakkalou, 2007), infants saw items only once, and image pairs were taxonomic sisters. The match between parental report and infant behaviour provides evidence of the item-level accuracy of both measures of lexical comprehension, and informs our understanding of how British parents interpret standardized Communicative Development Inventories (CDIs).