PSYstackhouseetal1997

Stackhouse and Wells (1997)

Copyright Notice: This material was written and published in Wales by Derek J. Smith (Chartered Engineer). It forms part of a multifile e-learning resource, and subject only to acknowledging Derek J. Smith's rights under international copyright law to be identified as author may be freely downloaded and printed off in single complete copies solely for the purposes of private study and/or review. Commercial exploitation rights are reserved. The remote hyperlinks have been selected for the academic appropriacy of their contents; they were free of offensive and litigious content when selected, and will be periodically checked to have remained so. Copyright © 2002, Derek J. Smith (Chartered Engineer).

First published online 13:26 23rd October 2002

This version [v1.0] dated 13:26 23rd October 2002

The Stackhouse and Wells (1997) Psycholinguistic Model

See firstly the supporting commentary for this material, and the omega series of models.

This is a recent attempt to show the sequential emergence of adult language processing modules during infancy and childhood. It is a combined effort by the speech and language therapist Joy Stackhouse and the clinical linguist Bill Wells, both of Sheffield University, and is expressly intended for use as a clinical aid in assessing and treating childhood speech and language problems. Here are five of the developmental stages the authors identify and discuss:

The Stackhouse and Wells (1997) Model - First Developmental Phase: The model begins as a fairly conventional inverted-U shaped omega diagram, at about the same level of complexity as Wundt (1902). Working clockwise from the acoustic input (bottom left), the following processing stages are encountered:

Peripheral Auditory Processing: This is where input sound is analysed for its component physical attributes of frequency and intensity, and rates of change thereof.

Speech / Non-Speech Discrimination: This is where input sound is classified as speech or non-speech before any attempt is made at word recognition (which does not take place until the Lexical Representation stage below). This stage is peculiar to the Stackhouse and Wells model, and is not found in Ellis (1982), Ellis and Young (1988), or Kay, Lesser, and Coltheart (1992). The authors justify making this a separate processing stage by citing cases of children with acquired language disorders who cannot distinguish speech from non-speech, but who nevertheless retain normal auditory acuity.

Phonological Recognition: This is where speech sounds are classified as belonging to a language which is familiar, or not. The authors suggest this is similar to tuning a radio through a succession of different language broadcasts until you locate one you recognise.

Phonetic Discrimination: This is where unusual input sounds are processed if speech strays from straightforward and normal. Note how the authors have set this resource off to one side of the main processing arch. They describe it as an "off-line processing unit", because it is not needed all the time. "This type of phonetic processing," they suggest, "can be called upon as circumstances demand" (p150), such as when a person is suddenly confronted by someone speaking in a different accent. They also give the example that English speakers can quite happily cope with a whole range of unusual sounds like the clicks used to encourage horses or when "tut-tutting" someone.

Lexical Representation: This is where whole known words are stored. In due course, this process will evolve into an important cluster of subprocesses, but at this stage is shown as a single box, and should be thought of as linking heard words (a) to the ability to speak them, and (b) to the ability to understand them. [In other words, it is a single box compression of the five central boxes on the PALPA, for use by inexperienced minds which have not yet learned how to separate the functions.]

Motor Execution: This is where "the [phonatory] gestures required for the accurate pronunciation of the word" (p153) are produced in the form of overt muscular activation.

[Stackhouse and Well's 1997 Model - First Phase]

The Stackhouse and Wells (1997) Model - Second Developmental Phase: The Lexical Representation process of the first developmental phase has now been replaced by three component subprocesses, as highlighted in blue (the processes outside the blue box have not changed), reflecting the growing sophistication of the lexical system. The three new components are:

Phonological Representation: This is the equivalent of the Phonological Input Lexicon in the PALPA, and is where whole words have a previously stored entry recording how they sound. The authors give the example of /mau s/ for MOUSE.

Semantic Representation: This is where the meaning of a word is stored. The authors give the example "[MOUSE] a small rodent, with long tail, fond of cheese, dwelling in skirting board etc" (p157).

[NB: the general feeling amongst cognitive modellers is that semantic representation involves some very diffuse storage mechanisms, spread across both cerebral hemispheres. The box sizes therefore reflect neither anatomical proportion nor localisability.]

Motor Program: This is the equivalent of the Phonological Output Lexicon in the PALPA, and is where whole known words have a previously stored entry for the motor commands required to produce the necessary sounds. These commands are then turned into muscular activation patterns at the Motor Execution box, as already described.

[Stackhouse and Well's 1997 Model - Second Phase]

The Stackhouse and Wells (1997) Model - Third Developmental Phase: The Lexical Representation processing cluster of the second developmental phase has now been extended by a further three component subprocesses, as highlighted in blue (the processes outside the blue box have not changed), reflecting even greater sophistication of the lexical system. The three new components are:

Orthographic Representation: This is the equivalent of the Orthographic Input Lexicon in the PALPA, and is where whole words have a previously stored entry recording how they look in print.

Grammatical Representation: This is the process which responds to the grammatical functions of a heard or seen word, and which, in turn, dictates how spoken or written words are used within the context of a sentence. For example, the word "mice" would be classified grammatically as an "animate count noun, with irregular plural form" (p157). [It can not, therefore, be used as a verb ("to mice"; "to mice someone"; "we miced", etc.), an adjective ("extremely mice of you"), adverb ("micely done"), and so on.] This aspect of lexical processing is peculiar to the Stackhouse and Wells model, and is not explicitly accounted for by the Ellis (1982), Ellis and Young (1988), Kay, Lesser, and Coltheart (1992), or Garrett-type speech production models.

Orthographic Program: This is the equivalent of the Orthographic Output Lexicon in the PALPA, and is where whole known words have a previously stored entry for the motor commands required to write or type it. It may be thought of as a computer program for writing (or typing) the letters <m o u s e> in the correct sequence.

[Stackhouse and Well's 1997 Model - Third Phase]

The Stackhouse and Wells (1997) Model - Fourth Developmental Phase: This developmental phase now allows the lexical representation to be bypassed by a motor programming process, as highlighted in blue (the processes outside the blue box have not changed). This reflects the fact that children gradually become more sophisticated at output processing, and underlies the important abilities of manipulating phonological units on demand in their own right (that is to say, divorced from all the usual lexical aspects). The following new processing stage has now been added:

Motor Programming: This is where internal sound representations can be deliberately manipulated to produce words not previously known, and therefore not in the lexicon. The authors give the example of the rapid production of rhymes, which readily produce both non-words and real words (eg. "cat - mat - gat" as rhymes to the target "fat").

[Stackhouse and Well's 1997 Model - Fourth Phase]

The Stackhouse and Wells (1997) Model - Fifth Developmental Phase (The Complete Model): The last process to be added (blue highlight) is that of motor planning. This is the level of processing "where the motor programs of the individual words are assembled into a single utterance" (p165). The following new processing stage has now been added:

Motor Planning: This is where motor programs from either the lexical or non-lexical routes "will be influenced by factors such as: how quickly the word is to be spoken; whether it is to be spoken with an expressive intonation, with wide pitch movement, or in a whisper; whether it is to function as a question [] or a statement" (p165). The end result is a "single utterance plan" (p165), which is then turned into muscular activation patterns at the Motor Execution box, as already described.

[Stackhouse and Well's 1997 Model - Fifth Phase]

References

Stackhouse, J. & Wells, B. (1997). Children's Speech and Literacy Difficulties: A Psycholinguistic Framework. London: Whurr.

Recommended Reading

"Children's Speech and Literacy Difficulties"

Stackhouse and Wells (1997)

To see an abstract, or to order this book, click here

No jacket view available