Describe the sequence of language development during the first two years, and give an example of each type of communication. Why does this sequence develop in this way?

What will be an ideal response?

A good answer would include the following key points:
- Language begins with prelinguistic communication. Before an infant can speak, she or he nonetheless makes vocalizations that have communicative power. For example, cooing, crying, gurgling, murmuring, and other noises are often made in response to relevant environmental stimulation.
- Babbling next takes place, around the age of 2 to 3 months. An infant repeating "bee-bee-bee-ba-ba-bee-bee-ba" would be an example.
- First words are usually spoken around the age of 10 to 14 months, although they could be earlier or later in particular children. Single words, such as "kitty" or "Dada," predominate until about 18 months of age.
- Holophrases represent the next stage, where single words signify entire concepts. "Ma" for "I want my mother to come near me now" would be an example.
- Two-word sentences appear at about 18 months, followed by telegraphic speech a little later.
- The progression outlined here is logical. Infants can't start communicating with full, grammatically correct sentences, but rather must build on a steady platform of advances: sounds, to words, to communicative words, to two-word utterances, to sentences. All the while, vocabulary is growing at a fabulous pace, and linguistic production advances steadily over this period.