This study focuses on parental use of parentese: the acoustically exaggerated, clear, and higher-pitched speech produced by adults across cultures when they address infants. While previous research shows that parentese enhances language learning and processing, it is still unclear what drives the variability in the amount of parental parentese use. We report on the development of a survey related to parental beliefs, knowledge, and self-awareness of parentese, and the cross-validation of this survey with daylong recordings in which parental parentese was measured through observation. Forty mother-father (18 monolingual English and 22 bilingual Spanish/English) U.S. families with infants between 3 and 24 months of age participated. Scores on the parentese questionnaire showed wide variability, suggesting that many parents were unsure about the effects of parentese on infant language development, and had limited self-awareness of their own parentese use. Almost half of the parents claimed that they talked to their child 'like an adult', and a similar number disagreed with the claim that parentese can support language learning. Our observational assessment of parentese demonstrated that all mothers and all fathers used parentese when talking to their infants; mothers in an average of 81% and fathers in an average of 69% of child-directed segments. Importantly, maternal parentese knowledge/beliefs scores, as well as their self-reported parentese use, were significantly positively correlated with observed parentese use; these relations were not significant for fathers. These results demonstrate that maternal and paternal links between beliefs, self-awareness, and behavior may be distinct, emphasizing the importance of studying all caregivers and using observational methodologies. More broadly, a thorough understanding of the factors that shape infants' language environments contributes to theories of language acquisition and can aid in intervention design.