(2) Young children's special ability to detect syllable and word boundaries
Brown and Bellugi (1964) found that detection of stressed syllables is an important step
in the acquisition of basic units of meaning (morphemic units) [43, 44]. The "telegraphic
speech" of young children, with use of morphemic units in new contexts, appears to be an
important stage prerequisite to discovering the rules of syntax as the language areas of
the temporal and frontal lobes continue to develop in the third and fourth years of life .
(3) Verbal auditory agnosia - impediment to language learning
Rapin (1997) commented that some children with autism exhibit a "verbal auditory
agnosia" (VAA), and appear not to recognize syllable and word boundaries in rapid
streams of speech . Children with autism tend to use whole phrase fragments, often
out of context; this is the "irrelevant and metaphorical speech" described by Kanner in
his descriptions of children with autism in 1943 and 1946 [46, 47].
Note that after the first decade of life learning a new language "by ear" becomes
increasingly difficult. Auditory agnosia may be an affliction of everyone older than the
critical period of language learning. Young children easily learn a second language
without accent. That we become unable to hear or change the accent with which we
speak a new language learned even in early adolescence is a sign of verbal auditory
agnosia that is a normal affliction of adulthood. This affliction likely also prevents our
recognition of what a child with developmental language disorder is not hearing.