Bilingualism and cognition is a complex topic with research showing different effects over time. Early research from the detrimental period claimed bilingualism hindered intellectual growth, but studies had many flaws. The neutral period found no differences, but highlighted early flaws. Later additive effects research overcame flaws and showed bilingualism need not be detrimental. Recent research examines bilingual cognitive effects like divergent thinking, metalinguistic awareness, and field independence. Overall, the relationship between bilingualism and cognition depends on variables that must be carefully controlled and defined in studies.