The human mind at work


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Descriptive Linguistic

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The human mind at work

  2. 2.  Psycholinguistics is the area of linguistics that is concerned with linguistic performance – how we use our linguistic competence – in speech (or sign) production and comprehension. The human brain is able not only to acquire and store the mental lexicon and grammar, but also to access that linguistic storehouse to speak and understand language in real time. When we speak, we access our lexicon to find the words, and we use the rules of grammar to construct novel sentences and to produce the sounds that express the message we wish to convey. When we listen to speech and understand what is being said, we also access the lexicon and grammar to assign a structure and meaning to the sounds we hear.
  3. 3. Speaking and comprehending speech can be viewed as aSPEECH CHAIN, a kind of “brain-to-brain” linking, as shownbelow: Physiologic Physiologic Linguistic Acoustic Linguistic al al Level Level Level level level
  4. 4. THE SPEECH SIGNAL Acoustic phonetics is concerned with speech sounds, all of which can be heard by the normal human ear.When we push air out of the lungs through the glottis, it causes the vocal cords to vibrate; this vibration in turn produces pulses of air that escape through the mouth (or sometimes the nose). These pulses are actually small variations in the air pressure caused by the wavelike motion of air molecules.
  5. 5. The sounds we produce can be described in terms of how fast the variations of the air pressure occur. This determines the fundamental frequency of the sounds and is perceived by the hearer as pitch. We can also describe the magnitude, or intensity, of the variations, which determines the loudness of the sound.
  6. 6. An important tool in acoustic research is a computer program that decomposes the speech signal into its frequency components. When speech is fed into a computer (from a microphone or a recording), an image of the speech signal is displayed. The patterns produced are called SPECTOGRAMS or, more vividly, VOICEPRINTS.
  7. 7. •Spectogram alsoshows formants•concentration ofacoustic energy•Group ofovertonescorrespondingresonatingfrequency of the airin the vocal tract
  8. 8. SPEECH PERCEPTION AND COMPREHENSIONA central problem of speech perception is to explain how listeners carve up the continuous speech signal into meaningful units referred as “segmentation problem”. Another question is, how does the listener manage to recognize speech sounds when they occur in different contexts and when they are spoken by different people? This is referred to as the “lack of invariance problem”.
  9. 9. In addressing the latter problem, experimental results show that the listeners can calibrate their perceptions to control for differences in the size and shape of the vocal tract of the speaker.Similarly, listeners adjust how they interpret timing information in the speech signal as a function of how quickly the speaker is talking. These normalization procedures enable the listener to understand a [d] as a [d] regardless of the speaker or the speech rate as we might expect, the units we perceive depend on the language we know.
  10. 10. English can perceive theex. difference between [l] and [r] because these phones represent distinct phonemes in the language. Speakers of Japanese have great difficulty in differentiating the two because they are allophones of one phoneme in their language.
  11. 11. Returning to the segmentation problem, spoken words are seldom surrounded by boundaries such as pauses. Nevertheless, words are obviously units of perception. The spaces between them in writing support this view. How do we find the words in the speech stream?
  12. 12. A sniggle blick is procking a slar.
  13. 13.  You would still be unable to assign a meaning to the sounds, because the meaning of a sentence relies mainly on the meaning of its words, and the only English lexical items in this string are the morphemes a, is and –ing. The sentence lacks any English content words. You can decide that the sentence has no meaning only if you attempt (unconsciously and consciously) to search your mental lexicon for the phonological strings you decide are possible words. Finding that there are no entries for sniggle, blick, prock and slar, you can conclude that the sentence contains nonsense strings. The segmentation and search of these “words” relies on knowing the grammatical morphemes and syntax.
  14. 14. The catchased the rat
  15. 15. a similar lexical look-up process would lead you to conclude that an event concerning a cat, a rat, and the activity of chasing had occurred.You could only know this only by segmenting the words in the continuous speech signal, analyzing them into their phonological word units, and matching these units to similar strings stored in your lexicon, which also includes the meanings attached to these phonological representations. (This still would not enable you to understand who chased whom, because that requires syntactic analysis).
  16. 16. 1. Over lunch, your friend tells you a story about a recent holiday, which was a disaster. You listen with interest and interject at appropriate moments, maybe to express surprise or sympathy.2. That evening, another friend calls to invite you to a party at her house the following Saturday. As you’ve never been to her house before, she gives you directions. You listen carefully and make notes
  17. 17. BOTTOM-UP AND TOP-DOWN MODELSTop down processes proceed from semantic and syntactic information to the lexical information gained from the sensory input. Through use of such higher-level information, we can try to predict what is to follow in the signal. For example, upon hearing the determiner the, the speaker begins constructing an NP and expects that the next word could be a noun, as in the boy.In this instance the knowledge of phrase structure would be the source of information.
  18. 18. Bottom-up processing moves step-by-step from the incoming acoustic (or visual) signal, to phonemes, morphemes, words and phrases, and ultimately to semantic interpretation. Each step of building toward a meaning is based on the sensory data and accompanying lexical information. According to this model the speaker waits until hearing the and boy before constructing an NP, and then waits for the next word, and so on.
  19. 19. LEXICAL ACCESS AND WORD RECOGNITIONPsycholinguists have conducted a great deal of research on lexical access or word recognition, the process by which we obtain information about the meaning and syntactic properties of a word from our mental lexicon.
  20. 20. Several experimental techniques have been used in studies of lexical access:Lexical decision measures response time or reaction time wherein the assumption is that the longer it takes to respond to a particular task, the more processing involved.RT measurements show that lexical access depends to some extent on word frequency; more commonly used words (both spoken and written) such as car are responded to more quickly than words that we rarely encounter such as fig.
  21. 21. Semantic priming effect arises when semantically related words are located in the same part of the mental lexicon, so when we hear a priming word and look it up in the lexicon, semantically related, nearby words are “awakened” and more readily accessible for a few moments. (say the that the word nurse primes the word doctor)
  22. 22. One of the most interesting facts about lexicalaccess is that listeners retrieve all meanings of aword even when the sentence containing the wordis biased toward one of the meanings.The gypsy read the young man’s palm for only a dollar.
  23. 23. Palm primes the word hand, so in lexical decision about hand, a shorter RT occurs than in a comparable sentence not containing the word palm. However, a shorter RT also occurs for the word tree. The other meaning of palm (as in palm tree) is apparently activated even though that meaning is not a part of the meaning of the priming sentence.
  24. 24. Naming task, asks the subject to read aloud a printed word. The experiment suggests that people can do two different things in the naming task. They can look for the string in their mental lexicon, and if they find it, they can pronounce the stored phonological representation for it. They can also “sound it out”, using their knowledge of how certain letters or letter sequences are most commonly pronounced.For example: subjects read irregularly spelled words like dough and steak just slightly more slowly than regularly spelled words like doe and stake, but still faster than invented strings like cluff.