Transcript The Nature of Human Language

The Nature of Human
Language
Neurolinguistics: The Brain and
Language
Neurolinguistics
• The branch of linguistics that studies the
biological and neurological foundation of
language.
• Researches humans and other primates
• Often uses data from atypical or impaired
language users to understand the properties
of human language in general.
The Human Brain
• The cortex
– Makes decisions
– Initiates
voluntary and
involuntary
actions
– Houses our
knowledge of
language
The Human Brain
• Two hemispheres: left and
right
– Left hemisphere controls
right part of body
– Right hemisphere controls
left part of body
– Joined by corpus callosum:
allows two hemispheres to
talk to each other
• Language seems to be located
in the left hemisphere.
Lateralization in early life
• Lateralization = localizing specific functions to
one hemisphere or the other
• Left side of babies’ brains lights up when exposed
to language people are born with left side
controlling most language (right controls some)
• Plasticity in early life babies’ brains can adapt
if they need to (clip)
– Babies with left hemisphere removed show almost no
problems with language—right side takes over
– Adults with left hemisphere removed lose most language
function.
Aphasia
• Any language disorder that results from
brain damage (disease or injury).
• Damage to Broca’s area or Wernicke’s area
(left side of brain) seems to cause aphasia.
• Not usually total language loss.
• We study aphasiacs to understand which
parts of the brain control which parts of
language.
Aphasia
• Broca’s aphasia = damage to Broca’s area
– Affects a person’s ability to form a sentence
within the rules of syntax and find the right
words
– Agrammatic language: lacks function words
(articles, prepositions, pronouns, etc.)
– “Me go, er, uh, PT [physical therapy] none o’cot,
speech…two times…read…ripe…rike…uh
write…practice…get…ting…better.”
– Broca’s aphasia patient 9 months after stroke
and 5 years after stroke
Aphasia
• Broca’s aphasia:
– Confused by passive voice
– “The cat was chased by the dog.”
Aphasia
• Wernicke’s aphasia
– Syntax and grammar sound right, but the words
don’t make sense.
– Difficulty naming objects
– Use the wrong words or nonsense words:
– “I felt worse because I can no longer keep in mind
from the mind of the minds to keep me from mind
and up to the ear which can be to find among
ourselves.”
– “I’m a male demaploze on my own. I still know my
tubatoys what for I have that’s gone hell and some
of them go.”
What does aphasia teach us about
language and the brain?
• The brain makes connections between
semantically-related words (words that are
related in meaning)
– boy and girl, table and chair, cheer and clap
• The brain makes connections between words
that sound alike
– Pool and tool, sable and table, crucial and crucible
What does aphasia teach us about
language and the brain?
• Aphasiacs have difficulty speaking, but
don’t have any other impairments (hearing,
writing)
• Language isn’t centralized in one area of the
brain
• Hearing, grammar, and words are all located
in different parts of the brain.
The Critical Period
• The critical age hypothesis: the ability to learn a
native language develops between birth to
middle childhood
• Children don’t need specific language
instruction, but they need exposure to language.
• Language develops quickly and easily during
critical age, without intervention
• Children deprived of language develop
atypically.
The Critical Period
• Critical age hypothesis: tested by
experiments in nature
• “Genie”
– Confined in a room with minimal human contact
from 18 months – almost 14 years
– Knew no language, not able to speakalthough
language acquisition is a biologically-based
ability, it must be triggered by the environment
The Critical Period
• “Genie”
– Eventually able to learn large vocabulary
(concrete and abstract words)
– Never acquired a grammatical structure or
complex sentences
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•
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Man motorcycle have
Genie full stomach
Genie bad cold live father house
Want Curtiss play piano
The Critical Period
• “Genie”
– Tests showed language was localized to right
hemisphere
– Usual language areas atrophy because of lack of
stimulation
– Genie was a powerful nonverbal communicator
 language is not the same as communication.
The Critical Period
• Chelsea
– Deaf, wrongly diagnosed as mentally impaired
until age 31
– Fitted with hearing aides, received extensive
language training
– Had large vocabulary but never developed a
grammar
– Showed an equal response to language in both
hemispheres  language was never lateralized
– Critical period is true for grammar, but not
vocabulary