Humans
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2-year-olds don’t talk in sentences
but can still tell nouns from verbs
New brain study suggests that toddlers know basic grammar
By Bruce Bower
Two-year-olds know more about grammar
than they can say. Budding toddlers recognize the difference bet ween nouns and
verbs in simple sentences, even though
the kids don’t utter such sentences for at
least another year, say Anne Christophe
of the Laboratory of Cognitive Sciences
and Psycholinguistics in Paris and her
colleagues.
Children begin to use two or more
words at a time by age 2, but their statements are typically incomplete and show
no signs of grammatical knowledge. Yet
upon hearing a sentence in which a noun
incorrectly replaces a verb, or a verb
incorrectly replaces a noun, toddlers
display split-second brain responses
that signal awareness of the rule violations, Christophe’s team reports online
June 29 in Developmental Science.
Youngsters fitted with electrode caps
show characteristic brain responses
after hearing mixed-up nouns and verbs.
Electrical activity, mainly relegated
to the left-frontal brain, spiked when
toddlers heard nouns in a verb position. Electrical responses farther back
on the brain’s left side, in the temporal
lobe, jumped as toddlers heard verbs in a
noun position. Both patterns resembled
those that have already been implicated
in noun and verb knowledge in adults.
“This experiment suggests that brain
networks responsible for language processing get organized extremely early,
showing striking similarities with
the adult system long before children
start producing adultlike language,”
Christophe says. A basic grasp of native-language rules may assist youngsters in
learning the meanings of new words and
other elements of language, she says.
In contrast, some scientists suspect
that toddlers memorize a large repertoire
of verbal phrases before making generalizations about object and action words at
around age 3. A related hypothesis holds
that language learning depends partly on
a quantitative ability to notice features of
speech that regularly go together.
“Children could well have some basic
syntactic knowledge by age 2, which
continues to develop throughout early
childhood as they identify the statistical
regularities of their language,” remarks
psychologist Erik Thiessen of Carnegie
Mellon University in Pittsburgh.
Ancient Andean
civilization likely
spurred by maize
Farming the crop may have
led to an early state society
By Bruce Bower
Prehistoric communities in one part of
Peru’s Andes may have gone from maize
to amazingly complex. Bioarchaeolo-gist Brian Finucane’s analyses of human
skeletons excavated in this region indicate that people living there 2,800 years
ago regularly ate maize. This is the earliest evidence for maize as a staple food
in the rugged terrain of highland Peru,
he says.
16 | SCIENCE NEWS | August 1, 2009
Maize agriculture stimulated ancient
population growth in the Andes and
allowed a complex society, the Wari,
to develop, Finucane contends in the
August Current Anthropology. Wari
society included a central government
and other elements of modern states. It
lasted from around 1,300 to 950 years
ago and predated other Andes civilizations, including the Inca.
Scientists disagree about when and
how civilizations formed in the Andes,
but Finucane says his analysis indicates
that “intensive maize agriculture was
the economic foundation for the development of the Wari state.”
Finucane, now a law student at Yale
University, analyzed the chemical composition of bones from 103 individuals
excavated by other researchers at six prehistoric sites in Peru’s Ayacucho Valley,
one of several Andean regions where
early civilizations arose. Chemical signatures of substantial maize consumption
appeared in the bones of individuals from
every Ayacucho site, Finucane says.
Finucane “makes a strong case” for
maize as a key food in the Ayacucho Valley by about 1,800 years
ago, but not 2,800 years
ago as argued in his new
paper, remarks Yale
University anthropologist Richard
Burger, who was
not involved in
the study.
FROM TOP: LSCP, CNRS PARIS;
B. FINUCANE
A skull found at a roughly 1,000-year-
old Ayacucho Valley site in Peru’s
Andes yielded chemical evidence of
substantial maize consumption.
