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Functional Equivalence Hypothesis.

Functional Equivalence Hypothesis.

What is the Functional Equivalence Hypothesis? Use image scaling as an example (6pts)
What is bottom-up vs. top-down processing? Provide an example of each. (8pts)

 

The scientific and academic residential areas have long assumed that noticeable dialog (speechreading) can produce “functional” phonological representations of presentation in individuals for whom auditory dialog expertise is missing from delivery. Although it is acknowledged that precluded auditory access to spoken language limits deaf children’s abilities to learn spoken language phonology through hearing, it is widely speculated that other sensory processes (mainly vision) can, to varying degrees, compensate or substitute for inaccessible acoustic evidence in developing an internal representation of spoken language (Alegria, 1998; Campbell, 1987, 1997; Dodd, 1987; Hanson, 1982, 1991; Leybaert, 1993, 1998) and, in turn, a “functional phonology” that will then support reading acquisition (for a review, see Perfetti & Sandak, 2000). In this paper, we will call this position the functional equivalence hypothesis. In what follows, we will first briefly review the functional equivalence hypothesis, then examine existing evidence for it, and finally, present the current study aimed directly at examining the nature of phonological representations in deaf children. Throughout this paper, deaf children are those with a congenital or early-acquired severe to profound hearing loss (e.g., greater than 75 dB in the better ear) that precludes auditory perception of conversational speech. For these children, irrespective of communication method, access to the “continuous phoneme stream” of a spoken language is mediated through visual perception.

The functional equivalence hypothesis statements that deaf children’s phonological improvement is qualitatively related, albeit quantitatively late, as compared to listening to children (see Paul, 2001, for any assessment). The central claim of the functional equivalence hypothesis posits that visible speech information (seen articulatory gesture) extracted from the speech signal by the deaf learner is interpreted as a phonologically plausible signal by the brain (Campbell, 1987; Dodd, 1976; Dodd & Hermelin, 1977). This claim is based on theories of speech perception that propose that articulatory gestures (vocal tract movements) are the primitives or objects of speech perception (e.g., Fowler, 1986; Liberman & Mattingly, 1985). These theories posit that phonetic information derived from both auditory and visual inputs map into the same motor representation of vocal tract gestures. Thus, it is hypothesized that a common abstract phonological code underlies the phonological representations established in long-term memory irrespective of the modality (auditory or visual) through which they are activated. Indeed, Campbell (1990) proposes that whereas auditory and visual speech information may differ with respect to the phonetic information they afford, they do not differ in the phonological representation they activate. Visual speech then is seen simply as a degraded or informationally poorer phonetic form of the auditory-visual speech available to hearing children (for a review, see Leybaert, 1993).

For this schedule, this has been more recommended that through the help of the aesthetic information and facts acquired through speechreading (Campbell, 1987 Dodd, 1976 Dodd & Hermelin, 1977) and also the articulatory truly feel of words and phrases which comes through extensive conversation coaching (Marschark & Harris, 1996), deaf young children can get phonological representations of words. Finger spelling (Campbell, Burden, & Wright, 1992), learning to write (Hanson, 1989), and extended experience with words in print (Hanson & Fowler, 1987) are proposed as additional sources of information that can help deaf individuals to develop awareness of the phonological structure of words. Although it is generally agreed that no one source of information alone is sufficient, it is argued that in combination these sources of information contribute to developing the phonological representations that underpin the coding of words in the mental lexicon for deaf individuals (see review in Perfetti & Sandak, 2000). Difficulties in reading are then seen as a consequence of delays in learning and difficulties in accessing abstract representations for speech sounds (e.g., Alegria, 2004; Hayes & Arnold, 1992; Paul, 1998) and not as a result of underlying differences in the nature of the representations themselves.

Experimental data about the reflection of talked words phonological structure by congenitally deaf individuals is surprisingly rare given that the efficient equivalence theory is the key presumption directing instructional methods for deaf young children during the entire earlier century. Consequently, and in sharp contrast to current understanding of how phonological representations are progressively elaborated by children with intact hearing (see discussion in Werker & Yeung, 2005), our understanding of both the development and the level of specification of deaf children’s underlying representations is severely limited. Such a gap in our knowledge would appear to constitute the weakest link in determining the extent to which speech perception “in the absence of audition” may result in similarities and/or differences in the way that speech sounds are represented or processed between deaf and hearing individuals.

Typically, children’s phonological representations happen to be evaluated through management of measures screening their phonological consciousness abilities (Swan & Goswami, 1997). Previous studies of phonological awareness in deaf children have produced inconsistent results with some studies reporting “phonological effects” whereas others have found no such evidence (for a review, see Perfetti & Sandak, 2000). For the most part, studies reporting negative findings come from investigations of phonological awareness in young deaf readers (e.g., Izzo, 2002; Miller, 1997), whereas studies reporting positive findings come from investigations of older or skilled deaf readers (e.g., Hanson & Fowler, 1987; Hanson & McGarr, 1989). These observations are often interpreted as supporting developmental delay rather than deficit assumptions and a connection between higher levels of reading achievement and access to spoken language phonology (see review in Paul, 2001).

A careful consideration of the past analysis, having said that, gives several option factors of why the habits proof deaf individuals’ phonological understanding appears joined. First, although the studies have used a wide variety of different phonological awareness tasks, they have focused on a limited range of phonological structures (mainly rhyme). Critically, studies investigating phonological awareness have almost always (for an exception, see Sterne & Goswami, 2000) measured only one level of phonological structure and thus cannot provide evidence regarding the extent to which the developmental continuum in deaf individuals resembles that observed in hearing individuals—moving from awareness of larger units (syllables and rimes) to smaller units (phonemes; e.g., review in Swan & Goswami, 1997). Importantly, only a few studies (Izzo, 2002; Miller, 1997) have examined phonemic awareness (fine-grained contrast sensitivity) that appears to be a critical factor in both lexical acquisition (e.g., Werker & Yeung, 2005) and reading acquisition (e.g., Fowler & Swainson, 2004; Goswami, 2000) for typically hearing children. Thus, existing data offer little insight into the extent to which the well-documented difficulties that deaf children encounter in learning to speak (see review in Marschark, 2001) and learning to read (see review in Paul, 1998) may actually arise from deficits in the accuracy and the segmental organization of the underlying representations of words in their mental lexicons.