Science is nothing but developed perception, interpreted intent, common sense rounded out and minutely articulated. - -George Santayana, n.d.

This quote from the philosopher Santayana begins to explain some of the frustration many clinicians experience when they think about research. For example, why don't research results agree with one another? Why do things keep changing? How can two divergent points of view both be correct? How do I choose what to use? Well, none of these questions has an easy answer. Knowledge unravels slowly. Scientists begin to discover new knowledge because past investigations show them what to look for.

Beyond conveying the practicality of science, and hinting at the frustration, I think that the most important aspect of Santayana's quote is its reference to common sense. In my view, this is a reference to focusing on what is clinically relevant-things that can be applied in clinical practice tomorrow. Hence, the purpose of this issue of Topics in Language Disorders is to update the reader on the current trends in speech sound disorders by considering some foundational issues in assessment and treatment.

The issue begins with an article by Munson, Edwards, and Beckman, which describes the role of phonological representations in speech production and error typology. These authors divide phonological knowledge into four domains: perceptual knowledge, articulatory knowledge, higher-level phonological knowledge, and social-indexical knowledge. Perceptual and articulatory knowledge incorporates what a person knows about the different segmental and prosodic contexts in which speech occurs. As such, individual differences in the production of speech sounds can influence speech comprehension and production. Higher-level phonological knowledge focuses on identifying sound sequences within a language. In this case, the authors focus more on what an individual knows about word structure-that is, what sound combinations are permissible and which occur more frequently. The last category, social-indexical knowledge, incorporates linguistic variation as it relates to various social groups. The authors explore the role of these knowledge bases in the development of speech and in the explanation of speech sound errors.

The utility of stimulability in the assessment and treatment of speech sound disorders is reevaluated in the next two articles. Rvachew describes the controversy surrounding the role of stimulability in the selection of treatment targets; she presents data on the effectiveness of pairing phonemic perception with stimulable phonemes in the remediation of sound errors. This article is followed by a report of a clinical technique that focuses on stimulability. Glaspey and Stoel-Gammon illustrate a method, known as the Scaffolding Scale of Stimulability, which incorporates aspects of dynamic assessment to measure a child's growth in developing a target sound. These articles support previous notions about stimulability and propose ways to enhance the use of this procedure.

The next two articles focus on the influence of target selection. Tyler and Lewis describe how the consistency or variability of error substitutions influences treatment effectiveness. Their results suggest that the type of error pattern may be more reflective of the nature of a child's phonological representations than it is on the type of treatment needed for remediation. In a similar vein, Williams presents a case study to illustrate how assessment procedures, target selection, and intervention techniques interact with one another. She focuses on the individual needs of the child and how target selection is directly linked to understanding the child's phonological system. In other words, children seem to progress more quickly in treatment when the target focuses on an aspect of phonology that they are ready to learn.

The last two articles focus on the application of some of the more recently developed phonological theories in the assessment and treatment of speech sound disorders. These authors are suggesting new ways to look at error patterns. Bahr presents data on the use of speech gestures to differentially diagnose childhood apraxia of speech (CAS) from a phonological disorder. In this investigation, all of the children with speech disorders exhibited similar types of phoneme errors; however, the children with CAS evidenced longer word durations, which is believed to be reflective of motor speech planning difficulties. In the last article, Geirut and Morrisette demonstrate the utility of Optimality Theory in describing the error patterns of children with speech sound disorders. They describe error patterns in terms of constraints (i.e., things a child does not do) instead of phonological rules. This change in how errors are viewed can result in target selections that specifically meet the child's phonological needs and can result in the identification of processes that tend to co-occur. The idea here is to focus on facilitating change within the child's phonological system and not focus on individual phonemes.

All of the papers establish the complexity involved in selecting targets for remediation of speech sound disorders in children. The papers exhibit a balance between motor and linguistic approaches, and all focus on the necessity of considering the individual's needs, preferences, and abilities in the selection of treatment targets and intervention approaches. I hope that these articles will supplement your knowledge and stimulate new insights in your clinical work.

Ruth Huntley Bahr, PhD, Issue Editor

REFERENCE