Access to accurate, timely and age-appropriate information about menarche is an essential part of menstrual health. Reliable evidence shows that girls primarily obtain information from their mothers and/or other female family members, therefore, it is important to determine parents' knowledge and their predictions about other parents' knowledge of the age of menarche. To this end, we performed a pre-registered study with data collected from 360 households in Santa Rosa de Copán, Honduras. We

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... lemented a novel procedure to avoid social desirability bias whereby participants answered two separated questions: i) their knowledge about the age of menarche (self-report) and ii) to predict or guess the modal response of the other participants regarding the same question (modal guess). Participants were paid according to accuracy. Both questions appeared randomly in the survey. Results show that parents' knowledge is high in the study area. Recent studies indicate the age of menarche at 12 years old and 56.11% of the sample gave the same response while 62.78% hit the modal value. We estimated the impact of different sociodemographic variables and found only marginal differences. Interestingly, people with formal education and women tend to respond with lower predictions.