Children master language quickly and with relative ease, supported by both biological predisposition and reinforcement. B. F. Skinner (1957) proposed that language is learned through reinforcement, while Noam Chomsky (1965) argued that language acquisition mechanisms are biologically determined.

The critical period for language acquisition suggests that the ability to acquire language is at its peak early in life. As people age, this proficiency decreases. Language development begins very early, even before birth. Newborns show a preference for their mother's voice and can discriminate between their mother's language and other languages. Babies are attuned to the languages around them and prefer synchronized audio-visual language stimuli.

Initially, babies can differentiate among the sounds of all human languages. However, by around one year old, they can only discriminate among the phonemes used in their environment. After the first few months, babies enter the babbling stage, producing repeated single syllables. This babbling is not necessarily communicative and can occur when babies are alone. Babies exposed to sign language will also babble with their hands.

Children typically utter their first word between 1 year and 18 months, entering the "one-word" stage where single words carry larger meanings. Early vocabulary is often limited to familiar objects or events, primarily nouns. As children's vocabulary grows, they begin to form simple sentences and rapidly acquire new words. They also demonstrate an understanding of language rules, sometimes making mistakes through overgeneralization, such as saying "gooses" instead of "geese."

Children's language development follows a consistent pattern across different cultures and backgrounds, suggesting a biological predisposition for language acquisition. Here's an overview of the developmental stages:

1. 0-3 months: Babies engage in reflexive communication, responding to stimuli without intentionality.
2. 3-8 months: Reflexive communication continues, with an emerging interest in others and their interactions.
3. 8-13 months: Intentional communication and sociability develop as babies begin to understand that sounds can have meaning and purpose.
4. 12-18 months: The first words are typically spoken. These early words are often simple and related to familiar objects or people.
5. 18-24 months: Children start to form simple sentences of two words, combining basic concepts like "want cookie" or "big truck."
6. 2-3 years: Sentences become more complex, consisting of three or more words. Vocabulary rapidly expands during this stage.
7. 3-5 years: Children are capable of forming complex sentences and engaging in conversations. Their language use becomes more sophisticated, and they have a better grasp of grammar and syntax.

This progression from reflexive sounds to complex sentences illustrates the remarkable ability of children to acquire language, guided by both biological predispositions and environmental interactions.