Bilingualism

Individual and Societal Bilingualism
Per the "Encyclopedia of Bilingualism and Bilingual Education," "Bilingualism exists as a possession of an individual. It is also possible to talk about bilingualism as a characteristic of a group or community of people [societal bilingualism]. Bilinguals and multilinguals are most often located in groups, communities or in a particular region (e.g. Catalans in Spain).... [C]o-existing languages may be in a process of rapid change, living in harmony or one rapidly advancing at the cost of the other, or sometimes in conflict. Where many language minorities exist, there is often language shift...."
Foreign Language Instruction in the U.S.
According to language research consultant Ingrid Pufahl, "For decades, U.S. policymakers, business leaders, educators, and research organizations have decried our students’ lack of foreign language skills and called for better language instruction. Yet, despite these calls for action, we have fallen further behind the rest of the world in preparing our students to communicate effectively in languages other than English.
"I believe the main reason for this disparity is that foreign languages are treated by our public education system as less important than math, science, and English. In contrast, E.U. governments expect their citizens to become fluent in at least two languages plus their native tongue. . . .
"[F]oreign language instruction in the U.S. is frequently considered a 'luxury,' a subject taught to college-bound students, more frequently in affluent than poor school districts, and readily cut when math or reading test scores drop or budget cuts loom."

Language Development and Communication Disorders

Robert M. Kliegman MD, in Nelson Textbook of Pediatrics, 2020

Receptive Language Development

The peripheral auditory system is mature by 26 wk gestation, and the fetus responds to and discriminates speech sounds. Anatomic asymmetry in theplanum temporale, the structural brain region specialized for language processing, is present by 31 wk gestation. At birth, the full-term newborn appears to have functionally organized neural networks that are sensitive to different properties of language input. The normal newborn demonstrates preferential response to human voices over inanimate sound and recognizes the mother's voice, reacting stronger to it than to a stranger's voice. Even more remarkable is the ability of the newborn to discriminate sentences in their “native” (mother's) language from sentences in a “foreign” language. In research settings, infants of monolingual mothers showed a preference for only that language, whereas infants of bilingual mothers showed a preference for both exposed languages over any other language.
Between 4 and 6 mo, infants visually search for the source of sounds, again showing a preference for the human voice over other environmental sounds. By 6 mo, infants can passively follow the adult's line of visual regard, resulting in a “joint reference” to the same objects and events in the environment. The ability to share the same experience is critical to the development of further language, social, and cognitive skills as the infant “maps” specific meanings onto his or her experiences. By 8-9 mo, the infant can actively show, give, and point to objects. Comprehension of words often becomes apparent by 9 mo, when the infant selectively responds to his or her name and appears to comprehend the word “no.” Social games, such as “peek-a-boo,” “so big,” and waving “bye-bye” can be elicited by simply mentioning the words. At 12 mo, many children can follow a simple, 1-step request without a gesture (e.g., “Give it to me”).
Between 1 and 2 yr, comprehension of language accelerates rapidly. Toddlers can point to body parts on command, identify pictures in books when named, and respond to simple questions (e.g., “Where's your shoe?”). The 2 yr old is able to follow a 2-step command, employing unrelated tasks (e.g., “Take off your shoes, then go sit at the table”), and can point to objects described by their use (e.g., “Give me the one we drink from”). By 3 yr, children typically understand simple “wh-” question forms (e.g., who, what, where, why). By 4 yr, most children can follow adult conversation. They can listen to a short story and answer simple questions about it. A 5 yr old typically has a receptive vocabulary of more than 2000 words and can follow 3- and 4-step commands.