<P> Infants can distinguish native from nonnative language input using phonetic and phonotactic patterns alone, i.e., without the help of prosodic cues . They seem to have learned their native language's phonotactics, i.e., which combinations of sounds are possible in the language . </P> <P> Infants now can no longer discriminate most nonnative sound contrasts that fall within the same sound category in their native language . Their perceptual system has been tuned to the contrasts relevant in their native language . As for word comprehension, Fenson et al. (1994) tested 10 - 11 - month - old children's comprehension vocabulary size and found a range from 11 words to 154 words . At this age, children normally have not yet begun to speak and thus have no production vocabulary . So clearly, comprehension vocabulary develops before production vocabulary . </P> <P> Even though children do not produce their first words until they are approximately 12 months old, the ability to produce speech sounds starts to develop at a much younger age . Stark (1980) distinguishes five stages of early speech development: </P> <P> These earliest vocalizations include crying and vegetative sounds such as breathing, sucking or sneezing . For these vegetative sounds, infants' vocal cords vibrate and air passes through their vocal apparatus, thus familiarizing infants with processes involved in later speech production . </P>

When is an infant's first word typically spoken