Perception Of Continous Speech
Speech normally occurs in conversations with meaning and substance, and people listen for the massage, not the sounds. This is quite unlike the situations just reviewed in wich people identified single syllables heard in isolation for sound rather than massage. This disparity should make us wary. Are the theories of isolated speech sounds adequate for continuous speech? The answer turns out to be no. Then what is the relation between these two types of perception? One possibility is that the perception of continuous speech use all the processes of the perception of isolated speech sounds and then some. A more troublesome passibility is that the two kinds of perception are in certain ways fundamentally different. Althought the verdict is not yet in, the second of these two possibilities is still too real to dismiss out of hand. Consider the hypothesis that the perception of continuous speech is identical to the perception of isolated speech sound. This hypothesis is demolished by some of the earliest work on speech perception. G miller, Heise, and Lichten (1951) had people try to identify words in various amounts of white noise. The words were presented to some people in five-word sentences were identified more accurately. When the speech and noise were equally loud, for example, the difference amounted to 70 percent versus 40 percent words correctly identifed. Miler and his colleagues atributed this difference to the greater predictability of the words in sentences where syntactic and semantic constrints helped people rule out what words could occur where. As further evidence for this view, they showed that people were much more accurate in identifying words from a known list of 2,4, or 8 words than from a know list of 32, 256, or 100 words. The smaller the list, the more predictable the words, and the more predictable the words, the more accurately they were heard and identified. Later G Miller and Isard (1963) demonstrated that syntax and semanties make separate contributions to the identifications to the identification of words in sentences. They had people listen to three different types of sentences:
- Grammatical sentences, like Accidents kill motorist on the hoghways.
- Anomalous sentences, like Accidents carry honey between the house.
- Ungrammatical strings, like Around accidents country honey the shoot.
Note that grammatical sentences adhere to both syntactic and semantic constraints, anomalous sentences to constrains on word order but not meaning, and ugrammatical strings to neither. The sentences were specially constructed so that the same words occurred in all three types of sentences equally often. No matter what the level of noise in which the sentences were heard, people were most accurate on grammatical sentences, a little less accurate on anomalous sentences, and least accurate on ugrammatical strings. Once again, the more predictable the word, the more often it was identified correctly.
The active view of speech perception
How are these findings so to be accounted for? There are two models one might turn to, the active and the passive. In actually they lie at the ends of a continuun of models. Under the simplest passive model listeners try to identify each word as if it were an isolated word, and whenever they fail, the guess. The more predictable the word is from syntax and meaning, the more likely they are to guess it correctly. Under this view, listeners try to identify each word as if it were an isolated word, and whenever they fail, the guess. The more predictable the word is from syntax and meaning, the more likely the are to guess it correctly. Under this view, listeners make use of word predictability, not in the actual perception of the words, but only in their guesses when their perception has failed. The problem with this model is that listeners do much better than it predicts they should (see G. Millerand isard, 1963). Listeners could not gouess correctly often enough to identify sentences as accuratelly as they do. The active end of the continuum has more appeal. Under the active view listeners use linguistic constraints in the actual perception of the sentence. It is as if they listen for some words or phrases and not others, as if they are optimally ready to perceive some sounds and not others. The analysis by synthesis model is one active model of speach perception. Listeners synthesize words to match what they heard and succed when they synthesize words to match what they hear and succed when they synthisize a wor that truly matches. Linguistic contraints aid his process by norrowing down what they synthrsize. They thereby come up with the correct match more often. The appeal of the active view is that it accounts quite naturally for a series of quite. The appeal of the active view is that it accounts quite naturally for a series of quite extraordinary perceptual phenomena.
Again And Again I say hopefully this article can be useful for the readers
