Language processing
What are the components of
language, and how do we process
them?
Phonemes
• Most basic components of a language.
• Individual sounds
• What are the phonemes of English?
• What distinguishes them from each other?
Phoneme processing
• Perception
• Speed: Can process 15-20 phonemes per second
• Categorical Perception: Speech sounds get
categorized as one phoneme or another. No inbetween. Ex: ‘r’ vs. ‘l’ to a Japanese speaker
• Production
• Co-articulation: We change the phonemes we
actually use based on the other phonemes
surrounding it in the speech stream
Morphemes
• Smallest meaning carrying units in a language
– Root Words: simple words like “book”, “run”, etc.
– Affixes: Things we attach to words to modify their
meaning; “-s” for pluralization, “-ed” for past
tense, etc.
– Interesting note: While we have standardized the
spelling of morphemes when written, that doesn’t
mean they are always pronounced the same.
Morpheme processing
• Lexicon
– Content morphemes: Morphemes that actually
mean something. “-s”, “run”, etc.
– Function morphemes: Morphemes that serve a
gramatical purpose, but have no real meaning.
“the”, “or”, etc.
– People know roughly 80- to 100-thousand
morphemes, stored in the lexicon.
Neurology of the Lexicon
• Aphasias are deficits of language arising
from brain damage. They differ from
agnosias in that patients can still exhibit
non-linguistic knowledge of an object.
– Semantic paraphasia is where patients make
errors in production by substituting
semantically related words to the one intended.
– Semantic dementia: Progressive semantic
disorder largely associated with damage to the
left inferior temporal lobe.
Broca’s aphasia
• Patients tend to have significant deficits in speech
production; sometimes limited to producing only a
single word or syllable.
• Even in less severe cases, production of function
words is severely diminished.
• Also have a hard time understanding more
complex syntactical structures, such as passive
constructions.
• Corresponds with damage to the left inferior
frontal lobe.
Wernicke’s aphasia
• Patients experience significant difficulties in
understanding either written or spoken speech.
• Speech production is fluent and grammatical, but
nonsensical.
• Single word production tends to exhibit semantic
parahpasia.
• Wernicke’s area is located in the posterior
temporal lobe.
Conduction aphasia
• Neural pathways in the arcuate fasciculus
connect Wernicke’s area to Broca’s area
(one-way).
• When this pathway is damaged, patients
have difficulties with word usage.
• The also have difficulties repeating things
they heard, or spontaneously generating
speech.
Syntax
• Syntax (grammar) is the set of rules for
combining morphemes. It gives language its
meaningful structure.
• Are all languages derived from a common
universal grammar?
– Chomsky thought so.
Phrase structure grammar
• Phrase structure rules are rules for deconstructing
complex symbols into sets of simpler symbols.
•
•
•
•
S
NP
VP
det
-> NP VP
-> (det) (AdjP) N (PP)
-> (AdvP) V (NP) (PP)
-> a, an, the
• Knowing the phrase structure of a sentence allows
us to disambiguate it:
• They are cooking apples.
• Bob greeted his friend by the mailbox
Transformational grammar
• Chomsky said phrase structure grammars
were too simple.
• How can we capture the semantic
equivalence of syntactically different
sentences?
• Bob threw the frisbee.
• The frisbee was thrown by Bob.
Neurology of syntax
• Agrammatic aphasia exists in patients who
do not appear to have semantic deficits, but
have significant difficulty in understanding
sentences.
• They largely produce very short,
agrammatic sentences similar to those of a
child.