PSYC20007 Lecture Notes - Lecture 11: Markov Chain, Lexicon, Connectionism
10 May 2018
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Lecture 11
- Word recognition: words as windows to meaning
- Language comprehension seems to take place automatically and effortlessly – we have no
aareess of haig to do athig
- This effortlessness is based on the recognition of individual words in the speech stream, or
in print.
- Words are physical objects (auditory or visual symbols) that signify the meanings of their
referents
- Word recognition (recognition of the physical forms of words) provides the window through
which we access meaning.
- The focus of this lecture is on the recognition of individual words, either in the speech
stream (part 1) or when reading (part 2). The recognition of individual words is essentially a
form of categorisation – we recognise individual tokens (instances/exemplars of a word)
produced in speech or text as (iconic) instances of a category of similar previous
experiences. The features that distinguish one word from another are actually based on
rather minimal perceptual distinctions between speech sounds (in speech) and letters (in
tet. For eaple, the distitio etee the spoke for of the Eglish ords laid ad
lathe is oeed a sutle differee i the artiulatio of the fial phoee, a
distinction that may not be made in another language (e.g., French does not make this
distinction). One of the core problems of word recognition we will consider today is how we
resolve the potential ambiguity between words that arises when such close distinctions
must be made when listening to speech (and reading). We will consider some basic
computational models of spoken and visual word recognition that implement particular
mechanisms for helping resolve such ambiguity in the input.
- Lexical memory and lexical access:
- Lexical → referring the processes involved in using words
- Lexical processes → processes that have to do with words and recognising words
and comprehending words
- Lexicon - mental dictionary
- Linguistic Modalities
- → Auditory - Spoken - Phonology
- → Visual - Written - Orthography
- → Visuo-spatial - Sign languages
- These linguistics modalities are for perceptual word forms (arbitrary signs) that map onto
concepts (semantics)
- Lexical access - the process whereby the memory for a specific word form is located,
opeed or atiated
- Words are perceptual objects. This makes them powerful tools for thinking with – we can
actually attend to the physical forms of words to help guide our thought processes, and we
a aipulate ords as phsial ojets as a eas for turig ideas aroud i our
minds. However, during the comprehension of spoken and written language we are often
lissfull uaare of the phsial fors of ords; istead, skilled laguage users see
through the phsial fors of ords to aess the eaigs that the referee – in this
sense, words are like idos through hih e see eaig seatis. I this leture
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though, we will be considering the processes that underpin the recognition of the physical
forms of words – i speeh e refer to the phsial fors of ords as their phoologial
for , i ritig, e refer to the orthographi for i sig laguages there is a gestural,
visuo-spatial form).
-
- Prosody: patterns of stress and intonation in a language
-
- Spoken word recognition:
- No gaps between spoken words
- • Segmenting the speech stream is a non-trivial task.
- • The speeh aefor has o siple orrespodee to the hite spae etee prited
words.
- • Neertheless, spoke ords are pereied as oheret, disrete, eets – auditory objects.
- When fluent in language, we hear the individual words
- Words in sentences are not separated from one another by clear pauses. Instead, speakers
run words together, making it difficult to tell where one word ends and another begins.
Indeed, the tendency of speakers to run words together has proven to be a formidable
hurdle for the development of speech recognition technology. Because listeners cannot
count on pauses between words, they must rely on other information in the speech signal to
indicate how word boundaries are marked. Learning which features mark word boundaries
in a particular language seems to involve discovering the way that sounds within words are
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typically ordered—phonetically and prosodically. These patterns differ from one language to
another. Consequently, learners must discover the sound properties that are the most useful
cues to word boundaries in their native language.
- • The ailit to seget the speeh strea despite oisi.e., iperfet, ariale iput
and great variability between speakers begins early in development.
- Prosodic cues to word boundaries:
- Infants [in first few months of life] tune into regularities in the stress-patterns of their native
language. The stress pattern (metrical rhythm) of a language is one element of the prosody
of the language [give clues where one word ends and the next word begins]
- About 90% of English multi-syllabic words stress the first syllable –pencil, stapler, trampoline
- This strong–weak (trochaic) pattern is the opposite to that used in languages such as Polish,
in which a weak–strong (iambic) pattern predominates.
- English includes some iambic words (e.g., guitar, disgust)
- All languages contain words of both kinds, but one pattern typically predominates.
- The dominant stress pattern (i.e., metrical pattern, or rhythm) within a language provides a
source of information (a statistical regularity) in the speech signal that assists listeners to
find the boundaries between words. However, there is a potential paradox with an account
such as this. How can a learner identify the predominant stress pattern of words in the
native language without already having some ability to segment fluent speech? One possible
explanation is that learners develop a bias for the predominant stress patterns of native
language words on the basis of words that they hear frequently spoken in isolation. For
example, names in English are most likely to begin with strong syllables, and those which do
not often have nickname forms which do. English learners have been shown to have some
ability to recognize the sound patterns of their own names by 4.5 months of age. In addition,
diminutive terms that are used frequently in addressing infants often have strong/weak
stress patters e.g., o, dadd, a, doggie, kitt, irdie, et. If this
account is correct, then in other languages, names and diminutives may also model the
predominant word patterns.
- Stress provides a prosodic cue to help infants identify potential words within the speech
stream
- At 7.5 months of age, English-learning infants can segment words from speech that reflect
the strong–weak pattern, but not the weak–strong pattern
- → For eaple, he ifats hear a phrase like guitar is the pereie taris as the ord-
like unit
- → Because guitar begins with an unstressed syllable, and is is a eak sllale.
- → Results based on measures of preferential looking time.
- Fro the astrat of Juszk et al., 1. A series of 15 eperiets as oduted to
explore English-learig ifats apaities to seget isllai ords fro fluet speech.
The studies i Part I foused o .5 oth olds ailities to seget ords ith strog/eak
stress patterns from fluent speech. The infants demonstrated an ability to detect
strong/weak target words in sentential contexts. Moreover, the findings indicated that the
infants were responding to the whole words and not to just their strong syllables. In Part II, a
parallel series of studies as oduted eaiig .5 oth olds ailities to seget
words with weak/strong stress patterns. In contrast with the results for strong/weak words,
7.5 month olds appeared to missegment weak/strong words. They demonstrated a tendency
to treat strong syllables as markers of word onsets. In addition, when weak/strong words
co-occurred with a particular following weak syllale e.g., guitar is, 7.5 oth olds
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Document Summary
Word recognition: words as windows to meaning. Language comprehension seems to take place automatically and effortlessly we have no a(cid:449)are(cid:374)ess of ha(cid:448)i(cid:374)g to (cid:862)do(cid:863) a(cid:374)(cid:455)thi(cid:374)g. This effortlessness is based on the recognition of individual words in the speech stream, or in print. Words are physical objects (auditory or visual symbols) that signify the meanings of their referents. Word recognition (recognition of the physical forms of words) provides the window through which we access meaning. The focus of this lecture is on the recognition of individual words, either in the speech stream (part 1) or when reading (part 2). The recognition of individual words is essentially a form of categorisation we recognise individual tokens (instances/exemplars of a word) produced in speech or text as (iconic) instances of a category of similar previous experiences. The features that distinguish one word from another are actually based on rather minimal perceptual distinctions between speech sounds (in speech) and letters (in te(cid:454)t(cid:895).
