Language acquisition: 0-12 months
Studies show that the stages of language acquisition from birth to age 5 and beyond in visual-spatial modality (sign language) and vocal-auditory modality (speech language) are not only in the same order but also on the same timeline.
0-3 months: the fourth trimester
In this period, babies produce coos and goos -- both vocally and manually.
0-4 months; marginal babbling
In this stage, baby learns to coordinate her/his motor skills.
Baby produces "vocal play" as well as "manual play". Babies from different cultures or linguistic environments and even deaf babies babble non-distinguished sounds.
7-10 months: canonical (syllabic) babbling
Canonical babbling is when babies produced reduplicated syllables.
In speech (vocal babbling), babies produce syllabic consonant-vowel repetitions. E.g. "dadadada", "babababa" and other meaningless sounds.
Babies, who are exposed to signlan, also do manual babbling, producing syllabic hold-movement repetitions. E.g. opening and closing hand repeatedly.
9-11 months: finger pointing
Finger pointing emerges at around 9 months and becomes communicative at 11 months.
10-12 months: sophisticated (variegated) babbling
Babies develop some fine motor skills, such as pointing, waving, and picking up small objects.
At this stage, pointing with index finger also began to emerge as early as 9-10 months or as late as 12 months. Pointing is a non-linguistic though communicative gesture apart from babbling and language.
At this "sophisticated babbling" stage, babies of English speaking parents babble constonant-vowel-constonant (CVC). On the other hand, babies of ASL-speaking families babble with more varied patterns.
From this stage, babies develop toward their first words at average 12 months. Although, at this stage a baby may utter a first referential word or a few first words, using simple handshapes or simple sounds.
12 months: one-word stage
Vocabulary development begins to gradually increase from the first birthday.