Lexical Processing Flashcards
What is the mental lexicon?
[definition] a theory of how words are learned, represented, produced, and understood (theory of lexical activity)
What is the classical view of the mental lexicon?
A “lexicon-in-the-head” view.
- frequency is the most robust predictor of lexical processing (and human performance)
- therefore conceptualized as repeated exposure to a given lexical unit (repeat exposure results in better entrenchment in memory)
- “counters-in-the-head”
What is the (semantic) network theory?
That there is word form-to-meaning (a pattern of activity in a network)
State some evidence for semantic network representations.
[priming studies] a subject responds faster to a target stimulus because a related stimulus appeared in the context
- duck primes goose; horse does not (latency tests)
- neural activity related to goose differs after duck than horse
- easier to access if lions have stripes than something else, because lion is close to feline which is close to tiger which is really close to stripes
What are the stages of word recognition?
- initial contact
- - perceptual input acts as an interface with and activates lexical representations - lexical selection
- - the activated lexical candidates are evaluated against the perceptual-sensory input - word recognition
- - candidate is selected - lexical access
- integration + comprehension proper
What is lexical access?
The process of identifying words and recovering word-related information from LTM
- most models of lexical access deal with activating word form information
- it very fast (speech ~ 5 syllables/second; print ~ 200 - 250 ms)
How does modality factor into processing models?
Most models assume modality specific input representations
– separate for auditory (Wernicke’s) and visual word processing (visual word form area near visual cortex)
What is the cohort model for lexical access?
That multiple candidates (word initial cohorts) are activated by onset.
- there is a uniqueness point at which the last compatible candidate wins
- all or nothing (not sensitive to frequency)
What role does competition have in these models?
ALL MODELS ASSUME COMPETITION!
– words can compete even if they do not share any segments (ie. shipping vs. ship inquiry; shipping and inquiry compete for the same portion of the utterance)
What is the TRACE model?
There are complex input representations (“pseudo-spectral” acoustic-phonetic features).
- these encode the degree to which the feature is found in the input
- units hypothesized at the featural, phonemic, and word levels are replicated at each level
- at any given time slice may activate several different phonemes
[lateral inhibition] – units that span the same portion of the input inhibit each other
[OVERALL]
There is immediate cascaded activation of input representations – competition (the strongest hypothesis wins!)
What is spreading activation?
Activation of similar words, essentially.
What is the neighbourhood activation model/how does it account for spreading activation?
Looks at global similarity rather than onset.
– so /cat/ is similar to /bat/ and /at/ but not /castle/, since the difference in phonemes is too large
How do cohort models incorporate spreading activation?
With onset similarity.
– so /cat/ will activate /cab/, /cap/, /castle/ and so on, but not /bat/ (because initial sound segment doesn’t match)
How does the TRACE model account for spreading activation?
With onset and rhyme overlap (activated even with onset mismatch).
– time is important! early activated words are advantageous over later activated ones (the more information that comes in the better); the selection in favouring the best candidate
What are some problems with processing speech?
- non-linearity!
- - co-articulation
- - assimilation
- - stops are actually silent - segmentation problem
- - speech does not have sequences of discrete sounds
- - the listener must have a way to assign a certain acoustic features in the input to a given segment - embedding problem
- - most long word have multiple short words embedded (so /unitary/ contains /unit/, /you/, /knit/, /it/, /tarry/, /air/, and so one) - lack of invariance
- - acoustic properties vary by context (speaker characteristics, phonetic context, speech temp, environmental noise, foreign accents, etc.)
What is categorical perception?
Acoustic continuum becomes discrete representations.
- many signals but few phonemes
- gradual physical change but abrupt perceptual change
Is human speech special then?
Yes and no.
[NO]
- there is categorical perception in animals (chinchillas and quails, for example)
- there is categorical perception of non-speech sounds as well
- - these point to a non-special sound-processing development (no argument for genetically determined speech-processing module)
[YES]
- innately guided learning processes
- - we instinctively pay more attention to certain aspects of the environment (ie. speech)
- - especially refined/detailed processing of speech sounds - infants come ready equipped with all possible sound inventories (??)
- - babies recognize contrasts they haven’t learned
- - up to about 6 - 7 months
- - at 8 - 10 they start making native language distinctions only
What is the McGurk effect?
A perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception!
- see mouth moving in a certain way can change how we hear phonemes
- shows that other domains can affect speech perception (no strict modularity)
What is the relationship between conceptual knowledge and knowledge about word forms?
NONE~~
- people can have seemingly intact knowledge of concepts/meanings but no ability to recover information about the word forms
- the brain’s response to words depends on properties of words and properties of task
Where is activity in the brain that is specific to words?
LEFT inferior parietal region
Where is activity in the brain that is specific to pictures?
RIGHT middle occipital region
How do concepts and knowledge about words related to semantics in the brain?
Conceptual knowledge (non-linguistic) and knowledge about words/word-forms (linguistic) combine to enable semantics/meaning when words are either heard or read or signed -- slight complication in considering exactly what a word is (definition)
What are some modality-specific representations in the brain regarding word types?
- more difficult producing nouns than verbs in speech
- more difficulty producing verbs than nouns in writing
– argues that DD results from differential impairment in modality specific output lexicons and makes reference to there being distinct grammatical categories of nouns and verbs
ADDITIONALLY there is differential activation of brain regions for categories (ie. animals [occipital] and tools [inferior frontal regions], or concrete words vs. function words)
What are some task effects on neural responses?
There is differential activation for passive viewing of words compared to staring at a fixation cross, and action generation (name the action the noun; ie. hammer).
- for passive viewing there is activation in the left and right occipital lobes
- for action generation there is activation in the left frontal lobe
