Perception of Language

Chapter 4

 Perception of Language

Introduction

                        This analysis of language comprehension into four levels of processing is for

            convenience of exposition it does not necessarily mean that we procces language in

            a strictly serial manner. As you might have anticipated from our discussion in Chap-

            ter  3, the question of serial versus parallel processing has been a major interest of

            researchers studyng the perception of language. We will return to this issue at

            several point during this chapter.

The structure of speech

            The procces of speech perception seems simple enough. Listeners must in effect,

            categorize the sounds  that they hear into one of the many classers of sounds that exist

            in their language. In fact the task is an extraordinarily complex one for two major

            Under normal listening conditions the speech we hear compeles with other stimuli

            for our limited processing capacity. Other auditory signals, such as a conversation

            accros the room or someone’s sneezing or burping, can interfere with the fidelity of

            the speech signal

Prosidic Factors

                        Strees refers to the emphasis given to syllables in a sentence. We use strees to

            Distinguish between the noun and verb forms of various words, such as project and

            Pervert  and between pairs such asblack bird.

                        Prosodic factors are sometimes called suprasegmentals. Supra means to be

            Above something; these aspects of speech lie over speech segments, providing

            a kind of musical accompaniment to speech. With prosodic variation in mind

            let us now turn to the smaller speech segments on which prosodic factorsare

            superimposed.

Articulotary Phonetics

The study of speech sounds is called phonetics, and the more specific study of the

pronunciation of speech sounds is called articulatory phonetics.

-          Place  of articulation

-          Manner of articulation

-          Voicing

Acoustic phonetics

researches was beginning to identify the relationships between the acoustics properties

of the speech signal and the perceptual experience of the listener, and it was thought

that the application of this knowledge to reading machines was just around the corner.

-          Spectrograms

-          Parallel transmission

-          Context-conditioned variation

Speech as a Modular System

The concept of modularity is an important concept contemporary cognitive psychology.

Some criteria modularity have been. A cognitive system is modular if it (1) is domain

specific  (2) operators on a mandatory basis, (3) is fast, and (4) is unaffected by

feedback.

The problem of invariance. We have already seen from the phenomenon of context-conditioned variation, that the relationship betweer acoustic stimulus and perceptual

Experience is complex in the case of speech.

Categorical perception  A number of experimental findings have been advanced to

support  the view  that speech is perceptually special, but the one that has received

the most attention has been the phenomenon of categorical perception.

Attentional processes   Categorical perception is not the only evidence for the modularity

of speech perception. Rand ( 1974)  performed an experiment in which a

formant transition was presented to one ear and its steady-state portion was presented

to the other ear. Although neither of these stimuli was speech, Rand reported that

listeners could “integrate” these two signals into a meaningful speech signal.

The Motor Theory of Speech perception

The notion is that listeners use implicit articulatory knowledge-knowledge about how sounds are produced-as an aid in perception. To some extent, this approach is motivated by the economy of using the same mechanism for buth perception and production. But the main rationale for the motor theory is that it deals effectively with the problem of invariance discussed earlier. Liberman and colleagues (1967) argue that although the relationship between

acoustic structure and perception is quite complex, the link between articulation and perception is more direct: sounds  produced in similar ways but with varying acoustic representations are perceived in similar ways.

Perception of Continuous Speech

            The convenient fiction of the speech sound in isolation. However, speech sounds

are embedded in a context of fluent speech. Since we know that the acoustic structure of

speech sound varies with its immediate phone context, it seems likely that broader aspects

of context, such as adjacent syllables and clauses, may play a significant role in our identification of speech.

Prosodic Factors in Speech Recognition

There is little doubt that prosodic factors such as stress, intonation, and rate influence

the perception of speech. They provide a source of stability in perception since we can

often hear these superimposed qualities at a distance that would tax our ability to

identify individual speech segments. For instance, we can detect the moods of persons

talking down the hall from the intonational contours of theirs speech but still not be

able to identify what they are saying. Similarly, other prosodic factors, such as speech

rate or tempo, are relabvely easy to detect. The sheer availability of prosodic information. Let us look at two cases of the way prosodic and segmental information interact: stress and rate.

Strees  One of the main acoustic cues to strees, in addition, is the intensity of the sound.

We distinguish between the two meanings of blackbird, for example, by detecting the

relative loudness of the first and second syllables.

Rate   Speakers modify their rates of production by the number and length of pauses

During utterances, as well as by the amount of time spent articulating the utterance. Miller

(1981) has documented the acoustic consequences of changes in speaking rates vowel duration

is reduced and the duration of the cues that signal various consonantal distinctions is also

modified.

Semantic and Syntactic factors in speech Perseption

Contest and speech recognition   As we have seen a word isolated from its context becomes

less intelligible it follows we vary semantic and syntactic aspects of this context, then we should find changes in the perceptibility of the speech passage. Isolated the influence of syntactic and

semantic information in continuous speech: (1) grammatical strings, (2) anomalous strings that

preserved grammatical word order, and (3) ungrammatical strings.

Phonemic restoration

This procedure led to a striking auditory illusion: listeners reported hearing the excised /s/! In addition, when told that a sound was missing and asked to guess which one, nearly all listeners

Were unsucesfful.

Mispronunciation detection  What happens when a perfectly ordinary sentence contains a minor phonetic error? For example, if you heard sentence (9), would you have noticed that the

First phoneme in the fourth word has been mispronounced?

The TRACE Model of Speech Perception

The TRACE model seems to provide a good account of many facts about speech perception.

Stiil, it is likely that both interactive and modular approaches will play a role in a complete account of language processing. This is  because there may well be limits on the kinds of

Interaction among levels that take place.

Perception of Written Language

In tis section we examine the early stages of visual language processing during reading. Reading, clearly, is amultifaceted and complex procces, and we cannot do full justice to

this complexity here. Rather, our approach will be selective in attemting to identify points of similarity and difference with the early stages of auditory language processing.

Different Writing Systems

An orthography is a method of mapping the sounds of a language onto a set of written symbols. Languages differ in their orthographics, but three main types maybe distinguished. A logography takes the word or morpheme as the linguistic unit and pairs the unit with some pictorial symbol called the logograph or character.

            The alphabet is a system in which each letter is supposed to represent a phoneme.

Any schoolchild knows that there are many exceptions to a one-to-one association between

Phonemes and letters. Some words such as know contain silent letters, and so forth.

Levels of Written Language Processing

Eye Movements During Reading

Some the overall reading of by:

-          Saccades

-          Regressions

-          Fixations

Perception of Letters in Isolation

Perseption of Letters in Word Context

The Nteractive Activation Model