51 Methodological Considerations in Employing the Continuous Discourse Tracking Procedure with Hearing-Impaired Adults L. le Roux, BA (Pretoria) Department of Speech Pathology and Audiology, University of the Witwatersrand, Johannesburg R.W. Turton, MA (Witwatersrand) Department of Psychology, University of the Witwatersrand, Johannesburg ABSTRACT This article addresses the various methodological issues involved in the use of the Continuous Discourse Tracking (CDT) procedure as a test instrument for evaluating communication efficiency in hearing-impaired adults. An overview of the potentially confounding variables associated with the CDT technique is provided and consideration isgiven to the reliability of this procedure with reference to areas requiring systematic investigation. It is proposed that the adoption of an alternative paradigm as well as interdisciplinary approach to test construction may facilitate a multi-dimensional perspective to the assessment of speechreading and communicative ability in the hearing-impaired population. OPSOMMING Hierdie artikel bespreek die verskillende metodologiese aspekte inherent aan die gebruik van die "Continuous Discourse Tracking" prosedure as 'n meetinstrument by die evaluering van kommunikasie-effektiwiteit by gehoorgestremde volwassenes. 'n Teoretiese oorsig van die moont- like kontaminerende veranderlikes wat met hierdie tegniek gepaardgaan, word verskaf. Vervolgens word die betroubaarheid van hierdie instrument indringend beskou met verwysing na navorsingsareas wat sistematiese ondersoek verg. Daar word voorgestel dat die aanvaar- ding van 'n alternatiewe paradigma sowel as interdissiplinere pogings wat betref toetskonstruksie, 'n multidimensionele benadering tot die evaluasie van spraaklees- en kommunikasievermoens by gehoorgestremdes kan bevorder. INTRODUCTION Recent advanced technology Has introduced a new era in inter- vention strategies with profoundly hearing-impaired indivi- duals, particularly for those postlingually deafened. South Africa has recently inaugurated a multi-disciplinary approach to the assessment and rehabilitation of these individuals (Miil- ler, 1988) which has sparked joff general interest in the poten- tial benefits of cochlear implants in particular. For the audiologist, whose role is crucial, these developments present exciting challenges. T h e profession is increasingly called upon not only to assess candidates for cochlear pros- theses, but also to recommend suitable alternatives, document the effectiveness of sensory devices and to provide for essential after-care services. These considerations, coupled with the current focus on quali- ty assurance in clinical practice, emphasize the importance of accurate measurement of speech communication in the pro- foundly hearing-impaired. In addition, there is an urgent need to adapt currently available test instruments and to construct test stimuli to meet local demands for culturally appropriate diagnostic tools. The objective of this paper is to consider critically one of the speechreading assessment techniques, namely the Con- tinuous Discourse Tracking Procedure, which has been wide- ly applied to the assessment and treatment of postlingually, Die Suid-Afrikaanse Tydskrif vir Kommunikasieafwykiniis, Vol. 37. 1990 profoundly hearing-impaired persons. An appreciation of this technique is essential in order to avoid mechanical application of this procedure and to encourage clinicians to become dis- cerning test users. THE ASSESSMENT OF SPEECHREADING ABILITY In reviewing the literature on speechreading assessment it is notable that, despite the absence of a conclusive theoretical framework for speech information processing, many innova- tive and radically different approaches have appeared during the last decade (e.g. Boothroyd, 1987 (cited in Montgomery & Demorest, 1988); Cronin, 1979; Middelweerd & Plomp, 1987). The absence of a viable model of speech perception has, never- theless, exerted a noticeable influence on the standard of speechreading instruments developed so far; Montgomery & Demorest (1988) view most of these as being of inferior quality and describe them as not meeting current psychometric re- quirements. This statement needs some qualification how- ever; it pertains specifically to the insufficient availability of psychometric data on existing measures, rather than to the inadequacy of the instruments per se. Fortunately, as a result of several developments, most re- searchers are positive about improvements in the standard of speechreading instruments. They base their optimism on the following: Θ SASH A 1990 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2) A LEGACY OF SOUND ADVICE AND EQUIPMENT PHILIPS HEARING AIDS AUDIOMETERS FM SYSTEMS Head Office: 1005 Cavendish Chambers, 183 Jeppe Street P.O. Box 3069, Johannesburg 2000. Tel: (011) 337-7537. R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 2) Methodological Considerations in Continuous Discourse Tracking Procedure w i t h Hearing-Impaired Adults 53 1) the recent strides which have been made in terms of model development (Massaro, 1987); 2) the advent of interactive videodisc technology which has opened up avenues for exploring new methods of testing and 3) the availability of test construction and evaluation techni- ques which hopefully will be increasingly used by experi- menters in this field during the stages of test develop- ment. At present, however, it is generally agreed that the researcher- clinician who strives to evaluate an individual's speechread- ing performance in a reliable manner, is confronted with an extremely complex task. THE CONNECTED DISCOURSE TRACKING (CDT) PROCEDURE One unique and highly versatile procedure which represents an alternative aproach to the measurement of speechreading skills in the hearing-impaired, is the CDT procedure, origi- nally described by De Filippo and Scott (1978). Tracking is a timed technique in which the talker (sender.) reads from a pre- pared text presented in a phrase-by-phrase manner. The receiver "listens" to each successive group of words as an entity, before repeating verbatim what the sender has said. If the receiver is correct, the talker proceeds to the next segment; if an error occurs in the repetition of the material, the talker and receiver employ various strategies to elicit a verbatim res- ponse. The goal of the procedure is to obtain a repetition that matches the text verbatim without the use of non-speech- related cues such as gestures (De Filippo & Scott, 1978). Track- ing performance is quantified and scored in terms of the number of words transmitted per minute (wpm). This procedure can be differentiated from traditional ap- proaches to speechreading testing on the following grounds: 1) It comprises a discourse task and therefore ongoing "meaningful speech" (and not isolated, single-word stimu- li-) is employed. J 2 ) / l t can be described as interactive in nature. Since the pro- cedure utilises a dyad and the talker's behaviour depends on the speechreader's performance, the interactive dyna- mics of a real conversation are allowed to play an impor- tant role in the evaluation. 3) The scoring deviates drastically from conventional pro- cedures in that the typically "all or nothing" approach to sentence scoring is not employed; rather, scoring results is a rate measure (although as a prerequisite a 100% accuracy is implied.) 4) The final wpm score relates to communication efficiency and, as such, represents a composite measure of com- munication rate. Therefore, in contrast with traditional measures, the wpm score reflects all the components within the communication interaction, namely the trans- mission, processing and correction as well as response time. In fact, De Filippo and Scott (1978) have suggested that this task not only taps perceptual skills (and the accu- racy thereof), but a combination of an individual's percep- tual and communicative abilities. Since the tracking technique's inception, it has been used with individuals of all ages and with a number of modifications for multiple purposes (Owens &iRaggio, 1987; Osberger, Johnson & Miller, 1987). As mentioned previously, its most extensive use has been in studies documenting changes in communica- tion efficiency as a result of sensory devices (Cowan, Alcan- ta, Blarney & Clark, 1988; De Filippo & Scott, 1978; Sparks et al. 1979; Muller, 1988). In addition, a number of studies [e.g. Danz & Binnie, 1983; Lesner & Kricos, 1987) have demon- strated its feasibility for intervention and training purposes. For the purpose of this article, discussions will be limited to the use of speech tracking with adults. APPEAL OF T H E SPEECH TRACKING PROCEDURE Since tracking is a live-voice procedure, it can be easily admi- nistered without the use of any equipment. In addition, it allows for quantification of the efficacy of the communication process. The procedure requires a different passage to be used at each session and therefore any learning of the test material is prevented. In view of the fact that ongoing speech is used in an interactive manner, "real-life" conditions are more closely approximated with use of the CDT technique; the task is therefore known for its high face validity (Levitt, Waltzman, Shapiro & Cohen, 1986). As with many of the tracking method's predecessors, the deve- lopment of this procedure seems to have arisen from clinical necessity. In retrospect, it is speculated that perhaps one of the major motivations for its development revolved around the aspect of repeated presentations. It seemed that the typical practice effects associated with perceptual tasks could be by- passed by means of this new technique. Although difficulties associated with traditional speechreading tests have to some extent been overcome by the speech tracking procedure and while other problematic issues are shared by conventional methods of speech recognition testing, it has now become apparent that this new procedure has introduced different sources of variability, which have often been disregarded by the clinical and research communities (for example, Hopkin- son et al. 1986). These methodological issues appear to contra-indicate the use of tracking for purposes of evaluation and in research inves- tigations employing an across-subject design(Lesner, Lynn & Brainard, 1988). A recent position paper by Tye-Murray and Tyler (1988) has been the first to review and identify formally the confounding variables specific to this technique. In addi- tion, in order to minimize the shortcomings associated with the use of this test instrument, these authors have proposed stringent guidelines for within-subject testing. CRITICISMS DIRECTED AT CONTINUOUS DISCOURSE TRACKING AS A TEST PROCEDURE The overall concern regarding the use of tracking as a test instrument pertains to one major aspect, namely that the ultimate score achieved by a receiver will vary as a function of several extraneous variables. Tye-Murray & Tyler (1988) maintain that these variables are almost impossible to control. As mentioned before, many of the problems associated with tracking as a test procedure are also relevant to the use of sentence-list speechreading tests. In their opinion, however, there are unique shortcomings specific to the use of the track- ing task. This has led these authors to conclude that the speech tracking procedure "does not reliably measure a receiver's ability to recognize speech" (Tye-Murray & Tyler, 1988, p. 227). In contrast De Filippo (1988) has argued that "for eva- luating speechreading performance tracking requires careful attention to the (very) same issues of assessment as any other Die Suid-Afrikaanse Tydskrif vir Kommunikasieafi