Some popular misconceptions about bilingualism include the ideas that bilingual children will not reach proficiency in either language and that they will be cognitively disadvantaged. Many studies in the early 20th century found evidence of a "language handicap" in simultaneously bilingual children, linking bilingualism with a lower intelligence. However, many of these studies had serious methodological flaws. For example, several studies relating bilingualism and intelligence did not account for socioeconomic differences among well-educated, upper class monolingual children and less-educated (often immigrant) bilingual children.