Speech Perception- A Foundation for First Language Acquisition

SPEECH PERCEPTION AND FIRST LANGUAGE ...

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Speech Perception- A Foundation for First Language Acquisition

Nasser Ghafoori Department of Literature and Foreign Langauges, Tabriz Branch, Islamic Azad University,

Tabriz, Iran

E-mail: [email protected]

Pardis Zaferani

Department of Literature and Foreign Langauges, Tabriz Branch, Islamic Azad University,

Tabriz, Iran

Email: [email protected]

Introduction

Perception is an action by which the mind refers its sensations to an external object as the

cause. While sensation takes place at the peripheral end organs, perception implies higher level

processing, and integration of sensations with past experience. It is a central process which is

mostly active, in the sense that thinking, or cognitive processing, dominates in the process rather

than anything physical, that is, Perception is the cognitive process of assigning labels to the

incoming signal. This is the case whether the signal is auditory or visual, or derived using any

other modality for sensing events in the world outside the human organism. (Thatham & Morton,

2011).

When investigating the child's acquisition of language, both auditory perception and linguistic

perception are important. Auditory perception refers to the processing of any auditory stimulus,

whether speech or non-speech, while linguistic perception implies the realization that the

auditory stimulus originated in the human vocal tract and carries meaning in that individual's

language system (Barker, 1982).

In the field of child language acquisition in general, and phonological acquisition in particular,

many researchers have queried the role of perception in the acquisition of phonology. Questions

have been raised about the relationship between perception and production. Does perception

facilitate production or vice versa? Is the child's phonological system before he begins to say his

mailto:[email protected]


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first words, or does perception follow a developmental pattern similar to production? What is the

nature of the child's representational system and how does it relate to the adult's representational

system?

Phonology is the branch of linguistics concerned with the study of speech sounds with

reference to their distribution and patterning. Any phonological system is composed to two

distinct levels, the phonetic level – referring to the actual production of speech sounds, and the

phonemic level- referring to native speaker's underlying representation of those elements in the

phonetic output which convey meaning. The child acquiring the sound of his language not only

learns to produce speech sounds, but also develops and underlying representation, in other

words, acquires both phonetics and phonology.

According to Moskowitz (1975 as cited in Barker, 1982), learning to produce and recognize

a wide range of sounds, is not the same as learning the contrasts between sounds which convey

differences in meaning. As Moskowitz suggests, learning contrasts between sounds which

produce differences in meaning is on aspect of the development of phonology. Phonology

emerges in conjunction with other aspects of developing language grammar, syntax, and above

all semantics; and language emerges in conjunction with other aspects of the developing child-

sensory, motor, physiological, and cognitive.

As the child interacts with his environment, he/she accrues experience and reaches certain

maturational levels in terms of physiology, social and cognitive functioning, and his system will

develop in a regular progression toward that of the adult. The child acquiring the sound of his

language not only learns to produce speech sounds, but also develops an underlying

representation, in other words, acquires both phonetics and phonology (Barker, 1982).


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Research in child development, speech perception and phonological development, adds to our

understanding of the role of perception in the acquisition of phonology (Chung, McBride-Chang

& Cheung, 2013).

Theories on Speech Perception

Speech perception is the process by which humans are able to interpret and understand the

sounds used in language. It is about how we recognize speech sounds and how we use this

information to understand spoken language. It involves a mapping from continuous acoustic

waveforms onto the discrete phonological units used to store words in the mental lexicon. For

example, when we hear the word cat, we map a complex and continuous pattern of vibration at

the eardrum onto a phonological percept which has just three clearly distinct pieces: /k/, /æ/ and

/t/. A great deal of evidence indicates that this mapping from sound to words is not a simple one-

step mapping, but is instead mediated by a number of different levels of representation (Phillips,

2011).

In many studies in linguistics, researchers have suggested that certain sound categories are

genetically-specified while others have determined that infants may be able to learn the sound

categories of their native language through passive listening, using a process called "statistical

learning". Statistical learning is when children pay attention to sequences and patterns that occur again

and again and by being attentive of those repeated patterns helps set up their phonological development.

Infants use statistical learning to learn the patterns of their native language (i.e. pattern detection).

Statistical learning is best characterized as Implicit. High frequency of reoccurring sounds.

Researchers have devised several methods to look at what infants can and can‟t perceive in

speech. They all rely on one essential observation – that infants, like adults, (a) react to changes

they perceive around them and (b) habituate to or get bored by repetitions of the same event


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(Clark, 2009). The main measures that have been used to demonstrate if infants detect changes in

phonetic features, have relied on:

Sucking-rates (infants suck harder and more frequently when they see or hear something

new)

Heart rate

Conditioned head-turns (infants readily learn to turn their heads towards a sound

accompanied by an image of an animated toy)

In each case, departures from the baseline rate are assumed to reflect a detection of

difference, of change, in the stimulus being listened (Clark, 2009). Newborns are able to

distinguish between many of the sounds of human languages, but by about 12 months of age,

their abilities weaken. As they age, there would be a need for different techniques to determine

infants' abilities in speech perception (Clark, 2009).

A theory of speech perception should ultimately account for the recognition of certain auditory

signals as speech, the processing of those signals from an initial frequency intensity duration

analysis to the psychological reality of the phoneme, and should include some reference to the

acquisition of speech perception by the child. "The general objectives of a theory of speech

perception are to describe the process whereby an acoustic signal is decoded in linguistic units."

(Stevens and House, 1972, p. 9).

Various models of speech perception have been proposed which view speech perception in

different ways and may have different goals in mind. Perception models can currently be

regarded as active or passive, depending on the degree of active involvement of the listener.


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- The Acoustic Theory of speech perception proposed by Fant (1962), views speech perception

as a passive process.

- The Motor Theory of speech perception (Liberman et al. 1967) is an active theory of speech

perception, involving participation by the listener in interpreting the incoming sound wave in

terms of basic units – sound segments. The motor theory defines speech perception

physiologically; perception is dependent on articulatory rules. Speech perception is possible by

recourse to the set of commands to the articulators necessary to produce the sound perceived.

- The Analysis by Synthesis Model of speech perception (Stevens & House, 1972) which is more

refined version of motor theory is an active theory of speech perception, involving participation

by the listener in interpreting the heard sound wave. It is originally developed as speech

synthesis model and has its roots in distinctive feature theory. The model "is based on the

premise that there exist close ties between the processes of speech perception and speech

production, and that there are component or operations that are common to processes" (Stevens

& House 1972, p.51).

- The Associative Store Theory of speech perception (Levinson 2005; Tatham and Morton 2006)

is a comprehensive, active theory which accounts for a number of observations about speech

perception. These include the following:

• The continuous acoustic signal is interpreted in terms of an underlying sequence of abstract

phonological units; abstract cognitive labels are assigned to the acoustic signal.

• A device is present which detects and traps errors of interpretation, and causes a reappraisal of

that portion of the signal which has been wrongly interpreted – interpretation error correction.

• Mechanisms exist to repair signals damaged before the interpretation process – production and

transmission error correction.


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Most of these models would agree that all auditory signals undergo initial peripheral

processing in terms of frequency, Intensity and duration, and that this initial processing is the

same for any auditory signal, whether it is speech or non-speech. Stevens and House (1972)

suggest that evidence from studies on the sensory systems of various animals shows that "fairly

complex processing takes place peripherally" (p.48). Disagreement arises as to the output of

peripheral analysis and the nature of further analysis.

Theories of Phonological Development

A theory of phonological development must meet several criteria. Every language has a

phonological system made up of a series of distinctive oppositions. A theory of phonological

development must account for the ultimate acquisition by the child, of all characteristics of the

adult system. It must be compatible with more encompassing theories of language acquisition,

and general development. The development of both the perception and production of phonetic

and phonological distinctions must be considered (Barker, 1982). Children have to learn to

distinguish different sounds and to segment the speech stream they are exposed to into units –

eventually meaningful units – in order to acquire words and sentences.

Here is one reason that speech segmentation is challenging: When you read, there are spaces

between the words. No such spaces occur between spoken words. So, if an infant hears the sound

sequence “thisisacup,” it has to learn to segment this stream into the distinct units “this”, “is”,

“a”, and “cup.” Once the child is able to extract the sequence “cup” from the speech stream it has

to assign a meaning to this word (Hoff, 2009). Furthermore, the child has to be able to

distinguish the sequence “cup” from “cub” in order to learn that these are two distinct words with

different meanings. Finally, the child has to learn to produce these words. The acquisition of

native language phonology begins in the womb and isn‟t completely adult-like until the teenage


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years. Perceptual abilities (such as being able to segment “thisisacup” into four individual word

units) usually precede production and thus aid the development of speech production.

A major controversy exists over the nature of the child's phonological system.

- Does the child have a system of his own, separate from the adult's, or is the child's internal

representation the same as the adult's, with the phonetic output limited by articulatory

constraints?

Theories of phonological development have been reviewed by Ferguson and Garnica (1975) and

divided into: behaviourist, structuralist, prosodic. Their review is summarized here.

The major proponent of the behaviourist theory is Mowrer (1956). The goal of the

behaviourist theory is to integrate phonological development with more general learning

theories. Interaction between caretaker and child, and selective reinforcement are important

factors.

The structuralist or linguistic feature theory, derived by Jakobson (1968), who attempts to

account for the acquisition of phonology with linguistic universals. Jakobson hypothesized that

the child learns phonological oppositions in an invariant order (a universal hierarchy of structural

laws), which is universally valid and starts with an optimal consonant and an optimal vowel.

Jakobson would support the hypothesis that the child has his own phonological system.

The prosodic theory proposed by Natalie Waterson (1971, 1987), in which emphasis is

placed on individual differences, in contrast to the structuralist theory, which emphasizes

linguistic universals. Here the individual child's specific input and the selective role of

perception are important factors. The child first attends to an utterance as a whole, and picks out

highly salient features. He builds a skeleton, composed of those features in the adult model that


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have high perceptual saliency. Initially then, the child's phonological system is limited by

perception.

Researchers often seem to be arguing at cross purposes.

The two notions 1) perception precedes production and 2) production is limited by

incomplete perceptual abilities, can be compatible. Development of perception may be in advance of

development of production, but may not be complete before the child begins to produce, and therefore

may affect productions. If the psychological reality of the phoneme is accepted, then ultimately a

developmental view of perception must be accepted, if Piaget' scheme of cognitive development is

followed, the child will not have an abstract underlying representation until approximately age 2, when

the sensorimotor period ends.

A Time Line of Speech Perception and Production

Figure 1 below was proposed by Kuhl et al in 2004 to show how the changes that occur in

speech perception and production in typically developing infants during their first year of life. It

presents how a child begins to process basic linguistic units, including phonological features,

phonemes, and syllables during the auditory input and articulatory output of spoken language. As

seen in the figure:


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Figure 1. Changes in speech perception and production in developing infants during their

first year of life (Kuhl et al, 2004).

Infants discriminate phonetic contrasts of all languages until they are 5-months old.

While 3 months, they can produce non-speech and vowel-like sounds.

As they are 6 months old, they are introduced to statistical learning (distributional

frequencies) and they have preference to language-specific perception for vowels.

At 7 months old, they start making 'canonical babbling' and

By 8 months, they detect typical stress pattern in words resulting from statistical learning

(transitional probabilities).

At 9 months old, they recognize language specific sound combinations and

By 10 months, they produce language specific speech production.

When infants are 11 months old, the consonant perception in foreign language declines

and there is an increase in their native language consonant perception.


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This time line is complete when the infant turns one year old. At this point, many infants produce their

first words. According to Kuhl (2004), Infants hear distinction of sounds until 6 months; they are citizens

of the world. They can discriminate all sounds of languages. Adults are not able to discriminate sounds

from other languages. Children become culture bound listeners extremely early before their first birthday.

They listen to vowel sounds and figure them out.

David Ingram (1976) discusses the acquisition of phonology in relation to cognitive

development. Stages of language acquisition are best seen within the "broader framework of the

child's cognitive ability" (p. 7).

Ingram suggests the following phonological stages:

1) Preverbal vocalization and perception (birth 1;0)

2) Phonology of the first fifty words (1;0 - 1;6)

3) Phonology of simple morphemes (1; 6 - 4; 0)

4) Completion of phonetic inventory (4; 0 - 7; 0)

5) Morphophonemic development (7; 0 - 12; 0)

Stage one includes babbling and infant speech perception. Ingram defines infant speech

perception as a nonlinguistic sensorimotor task.

Stage two is described as qualitatively different compared to later stages of development.

Contrary to Jakobson's belief that a system of contrasts emerges right away, Ingram

questions whether different forms are actually being used contrastively. During this stage

there are many "correct" forms which are simplified at later stages of development.

A large amount of the child's phonetic inventory is acquired in stage three, and a large

number of phonological processes are used.


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Completion of the phonetic inventory occurs in stage four. Fewer phonological processes are

used. Acquisition of morphophonemic rules is begun.

Stage five involves acquisition of complex morphophonemic rules which require the

cognitive development of reversible operations. An example is the use of contrastive stress in

English, e.g. b'lackboard, black'board.

Ingram's stages of phonological development show clearly that phonetic development is

complete long before phonological development.

Speech and Categorical Perception

Evidence from infant perception studies suggests that phonetic discrimination abilities are highly

sophisticated even at a very early age and that these abilities seem to be initially independent of

native language exposure (Jusczyk, 1997). Discrimination tasks assess the ability to perceive a

difference between two sounds and the listener is not required to give a label to the sounds in

question. In order to acquire adult phonological competence; however, the developing child must

not only learn to discriminate sound patterns, but also to organize these sound patterns

consistently into their appropriate phonemic category. This latter ability is often referred to as

“phonemic categorization” or “categorical labeling” in the speech perception literature (see

Simon & Fourcin, 1978).

The identification task used to assess the Speech perception categorization represents the

ability to group perceptually distinct sounds in the same category.

An early discovery about the nature of the innate skills that child brings to the task of phonetic

learning and about the timeline of early learning is called "categorical perception”. It is focused

on the discrimination of the acoustic events that distinguish the phonetic units.


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In speech, at the age of one month, infants can discriminate between /b/ and /p/ syllables and

/ba/ and /pa/. There are two tasks that are involved in demonstrating categorical perception.

These are called "identification and discrimination" (Kuhl et al, 1994). Experimentally we

determine categorical perception both by using identification tasks such as 'was that sound a /pa/

or a /ba/?' and with discrimination tasks such as distinguishin two sounds. (Scott. et al, 2010).

Speech Perception and Voice Onset Time (VOT)

Voice Onset Time (VOT) refers to the time interval between the release of a stop

and the beginning of vocal fold vibration. The possible existence of this interval is caused by the

fact that the voicing and closure mechanisms are distinct.

Children, like adults, after varying the VOT tables, showed poor discrimination with a

phoneme category but good discrimination across phoneme boundaries. Using the High

Amplitude Sucking Technique, it was suggested that children habituate to sounds within a

category. They would however increase their sucking rate when the sounds shift categories (/b/

to /p/), meaning that there was a novel stimuli, a dishabituation.

Native Language Magnet Theory (NLM) of Speech Development (Kuhl, 2008)

It is Patricia Kuhl who proposed the Native Language Magnet Theory (NLM) of speech

development to account for the influence of linguistic environment on speech perception (Kuhl

et al, 2008). NLM specify three phases in this development:

In phase 1, the initial state, infants are capable of differentiating human speech in all languages,

and these abilities derive from their general auditory processing mechanisms rather than from a

speech-specific mechanism.

In phase 2, infants‟ sensitivity to the distributional properties of linguistic input produces

phonetic representations based on the distributional „modes‟ in ambient speech input.


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In phase 3, the distortion of perception, which is the perceptual magnet effect, produces

facilitation in native and a reduction in foreign language phonetic abilities (Kuhl et al, 2008).

Infants are ready to learn any human language but their perceptual abilities adjust to their native speech

environment within the first year.

Mother’s and Speech Perception

Kuhl (2004) identifies motherese as a slower, more stressed, simplified, and repetitive version

of an adult sentence in the native language. When we talk to infants, we use this special language

which has a unique acoustic signature that promotes infants' processing of speech. When

compared to adult-directed speech, child-directed speech (motherese) is slower, has a higher

average pitch, and contains exaggerated pitch contours. In child-directed speech, prosodic cues

tend to be exaggerated in the kind of speech that is directed toward learning speech sounds.

Likewise, motherese helps infants to analyze the structure of speech by highlighting boundaries

between important units, such as words and clauses. Motherese has instructive meaning that it

conveys knowledge for infants during their critical period of language acquisition (Kuhl, 2004).

Study examined women speaking either English, Russian, or Sweedish and their voices were

recorded while they spoke to another adult or to their young infants. The research analyses

illustrated that the vowel sounds (the /i/ in 'see' and the /a/ in 'saw' and the /u/ in 'Sue') in child-

directed speech were more clearly articulated, because women were exaggerating all of the

acoustic components of vowels which benefited the infants (Kuhl et al. 1997). In contrast, in

adult-directed speech, there did not find any emphasis in the articulation. Motherese has also

been documented in a variety of cultures and across a typologically diverse set of languages,

including sign language (Kuhl et al. 1997).


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The Role of Prosody in the Development of Speech Perception

Empirical research suggests that prosody may help infants to segment speech and to help

locate grammatical units. Boundaries between important grammatical units such as clauses and

phrases are often marked by changes in variables related to prosody, including changes in pitch

contour, increases in syllable duration, and pausing.

It is Hirsh-Pasek et al (1987) who first examined whether infants respond to prosodic

marking of clausal units in fluent speech. They hypothesized that if infants are sensitive to

prosodic marking of clausal units, then they will listen longer to the versions with pauses

coinciding with the clause boundaries than those versions with the non-coincident pauses. The

procedure used in this test was the Head Turn Technique and there were groups of 6 to 9 month-

old infants. They both displayed significant listening preferences for the coincident versions,

concluding that the sensitivity to prosodic markers of clausal units is present in infants as young

as 6 months (Hirsh-Pasek et al, 1987).

Pre-linguistic Speech Perception and Speech Sound Discrimination Studies

DeCasper and Fifer (1980) found that newborns less than one day old preferred hearing their

mother's voice over listening to an unfamiliar female voice, suggesting that prenatal auditory

experience is involved. These researchers showed that newborns would suck more when hearing

their mother's voice compared to a stranger's voice. Procedures for testing speech perception

capabilities in young infants:

High Amplitude Sucking

In 1971, a study by Eimas et al. assessed 1-4 month old infants‟ abilities to discriminate between /ba/

versus /pa/ stimuli. They presented infants with between category shift sounds such as /ba/and /pa/, and


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the control group with within category shift sounds such as /ba/ and /ba/. Results showed that infants

increased their sucking rate after the between category shift and not after the within category shift.

This study demonstrates that infants, like adults, can perceive speech in a categorical manner, and this

technique therefore can be successfully used to describe discrimination abilities in very young infants.

Visual Habituation

The infant in this study can both be presented repeatedly with visual and auditory stimuli which can be

the syllable (/da/).

Infant's ability to categorize stimuli can be assessed using this method, and performance in habituation

tasks can be used as a predictor of information processing capacity. The procedure is based on the infant's

novelty preference and thus his/her visual attendance to a display when it is new. When an infant is

presented to the same display it will become familiar and it will no longer be novel and therefore an

infant's time will decline and the experimenter can infer that habituation has occurred. An infant, at this

point, will be presented to novel stimuli and watched to see if they can discriminate the old display and

therefore their looking time will increase.

The Conditioned Head Turning Procedures

The procedure tests the older infant's (ages from 6 months to 1 year of age) tendency to listen

to something new or to look at something interesting, like a moving toy. The infant sits on the

caregiver's lap across the table from an experimental assistant and he/she is shown brightly

coloured toys to keep their attention and interest. The initial sound is played repeatedly and then

changed, at which point the moving toy is presented. When the baby makes a correct head-turn,

the moving toy is displayed and the assistant smiles and praises the infant. When there is an

incorrect head-turn, there is no reinforcement (Slater, 1998).


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Conclusion

Infant's first perception of speech starts in the utero. It is filtered and the mother's voice is the

most familiar sounds of all other sounds. Many studies illustrate that one day old infants prefer

mother's voice to other female voices and they also show preference for stories frequently heard

while still in the utero. This indicates that infants are sensitive to prosody (Mehler et al, 1988).

For example, when a baby is born, their preference of hearing their native language eventually

becomes higher than other foreign languages. Infants detect contrasts from non-native language

before they turn one year old and they lose this ability afterwards. Infants also have pattern

abstraction capabilities where 6 month-olds can perceptually 'sort' novel instances of phonemes

into categories. They can detect similarity across different voices, intonation contours, and

phonological (co-articulary) contexts.

Path Kuhl is one of the only scientists who emphasize substantially on development of

speech perception and production. In 1992, she introduced the phenomenon called 'perceptual

magnet effect', which demonstrated that as a second language is acquired, the brain gradually

groups sounds according to their similarity with phonemes in the native language (Greenberg .et

al, 2006).

In summary, it may seem deceptively simple to acquire language however researchers have

struggled to explain the initial phases of how exactly infants can do this. At all levels, language

learning is constrained, meaning that perceptual, social and neural factors affect what can be

learned, how, and when. Identifying these constraints on infant learning and how they reflect

innate knowledge will be a continuing focus in the next decade.

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Speech Perception- A Foundation for First Language Acquisition

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