REVIEW

A framework for the conceptual modelling ofassistive technology device outcomes

M. J. FUHRER{*, J. W. JUTAI{, M. J. SCHERER} and F. DERUYTER}{ National Institute of Child Health and Human Development, National Institutes of Health,

Damascus, USA{ Department of Physical Medicine & Rehabilitation, The University of Western Ontario,

London (Ontario), Canada} Institute for Matching Person & Technology, Webster, NY, USA} Division of Speech Pathology and Audiology, Duke University Medical Center, Durham,

NC, USA

Accepted for publication: June 2003

Abstract

Purpose: A key step in planning assistive technology outcomesresearch is formulation of a conceptual model, specific to aparticular type of device, that provides a rationale for theexpected outcomes. This paper reflects the conviction that thedevelopment of device-specific causal models will be facilitatedby having available an overarching framework that ispotentially applicable to multifarious types of devices andtheir outcomes.Method: A literature review identified the critical, unmet needsfor a conceptual framework. The assumptions underlying theframework were specified preparatory to describing it anddiscussing its implications.Results: The outcomes of assistive technology devices aredepicted as resulting from the interaction among character-istics of a specific device-type, its users, and their environment.Initial junctures include procurement of a type of device and aperiod of introductory use that, interacting with variousmoderating co-factors, result in a variety of shorter-termoutcomes, possible longer-term use, and its outcomes.Conclusions: The framework has the potential of facilitatingthe development of device-specific causal models. It also maycontribute to developing a research agenda for assistivetechnology outcomes research by highlighting measures thatneed to be developed and by identifying testable hypothesesconcerned, for example, with the manner and duration ofdevices’ usage.

Introduction

The imperative of adopting the philosophy and meth-ods of evidence-based practice confronts many fields ofhuman service, assistive technology (AT) among them.A hallmark of that practice is a commitment to addres-sing consumers’ goals by integrating the expertise ofindividual service providers with the best availableevidence from systematic research. For the AT field, thatentails an emphasis on outcomes research that speaks tothe contributions that devices and the related servicesmake to users’ daily lives.

According to the comprehensive definition offered byGitlin,1 AT includes the following items: (1) structuralalterations (changes to the original structure of a physi-cal environment, e.g., widening doors in a house); (2)special equipment (attachments to the original structureof the physical environment, e.g., handrails, grab bars,and stair glides in the home); (3) assistive devices(applied to or directly manipulated by a person; e.g.,wheelchairs, reachers, voice-output communicationaids, and hearing or vision aids); (4) material adjustment(alterations to nonpermanent features of the physicalenvironment, e.g., clearing pathways, removing throwrugs, and adjusting lighting in the home); (5) environ-mentally-based behavioural modification (changes to aperson’s interaction with the physical environment,e.g., conserving energy in particular activities andsegmenting tasks to facilitate their execution).

In this paper, the term ‘AT’ is used to refer to thisentire spectrum of interventions. Consistent with theTechnology-Related Assistance for Individuals withDisabilities Act of 1988,2 ‘assistive technology device’

* Author for correspondence; M. J. Fuhrer, National Instituteof Child Health and Human Development, National Institutesof Health, 13 Kings Valley Ct, Damascus, MD, 20872, USA.e-mail: fuhrerm@mail.nih.gov

DISABILITY AND REHABILITATION, 2003; VOL. 25, NO. 22, 1243–1251

Disability and Rehabilitation ISSN 0963–8288 print/ISSN 1464–5165 online # 2003 Taylor & Francis Ltdhttp://www.tandf.co.uk/journals

DOI: 10.1080/09638280310001596207

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(ATD) refers mainly to assistive devices and specialequipment, as characterized above.

A serviceable definition of AT outcomes research issystematic investigation aimed at identifying the changesthat are produced by AT in the lives of users and theirenvironments. Those changes may range from improve-ments in delimited aspects of users’ motor, sensory, andcognitive functioning to enhancement of their socialparticipation, vocational productivity, and sense ofcontrol over their own lives. The cascade of outcomesmay extend to individuals’ environments as well andinclude, for example, a reduction in caregivers’ assis-tance and decreased costs to insurers and social welfareagencies.3

Huge strides in the growth of AT as an industry havenot been paralleled by a corresponding development ofresearch to assess the outcomes of those technologies.That shortfall can be attributed to a variety of factorsincluding (1) beliefs that the benefits of AT usage areself-evident, (2) willingness to rely on anecdotal reportsregarding its efficacy, (3) greater emphasis by AT devel-opers on demonstrating the technical performance ofnewly developed technology than on evaluating users’performance with it, (4) underdeveloped theories aboutthe adoption of AT and about its continued or discon-tinued use, (5) the sheer proliferation of technologiesand the means by which users access and adapt themto their individual life-styles, (6) the absence ofmandates to collect data about outcomes, and (7) insuf-ficient demand for that research from payers and otherstakeholders.

A paucity of appropriate outcome measures has beenidentified as being an additional barrier to conductingthe needed outcomes research.4 Many availablemeasures tend to be narrowly focused on particulartypes of AT and areas of user functioning, and to beincompletely developed from a psychometric viewpoint.The insufficiency of suitable measures is particularlyacute from the standpoint of a multiple-stakeholderview of AT and the related services.5 – 8 According to thatview, users’ expectations of outcome deserve foremostattention, but the expectations of other sectors are rele-vant as well. Included are users’ family members, friendsand co-workers, manufacturers and vendors, individualservice providers, service programmes, payers, rehabili-tation scientists, and policy makers taking a broad, soci-etal viewpoint. Those groups are viewed as differing tosome extent on the outcomes that they value, e.g., users’enhanced physical functioning and well-being, reduceddependence on others, enlarged sense of control overtheir own lives, increased options for social participationand work, or reduced consumption of health and social

services. Consequently, a variety of measures ofoutcomes measures may be called for if these differentoutcome expectations are to be addressed. Though anumber of candidate measures exist in collateral fields(e.g., geriatrics and social psychiatry), few precedentsexist for adapting them to the needs of research on AToutcomes.Progress in research on AT outcomes research can be

accelerated by capitalizing on advances in medical reha-bilitation outcomes research.9 Among those advancesare innovations in research design, measurement theory,and, most pertinent to the present paper, in stratagemsof planning outcome investigations.A cardinal planning stage is conceptualization of

target interventions and their outcomes. Consistent withnotions of rehabilitation treatment theory,10 this takesthe form of intervention-specific outcome models thatprovide a rationale for why particular interventionsachieve the outcomes set out for them. The focus of thispaper is on ATD-specific outcome models. By extension,they can be understood as being conceptual frameworksthat identify the features of ATD-types, services, users,and their environments that comprise the causalsequence connecting the procurement of devices tospecific outcomes. In essence, such models provideaccounts of how the use of devices is linked to theirhypothesized outcomes.Device-specific outcome models can markedly facili-

tate the planning and implementation of outcomestudies. The models can guide the selection of studydesigns, measures, and approaches to data analysis,especially the composition of multiple-regressionanalyses and structural equations. If confirmed bysound investigations, the models can contribute toidentifying the features of devices and services thatare associated with positive outcomes, provide testablepredictions about the users who will benefit from parti-cular devices, and provide useful clues to developingthe next generation of devices. Availability of a varietyof at least partially validated models will encouragesteps to abstract their common features and to inte-grate them into more generalized models. They in turncan be essential building blocks in theories of ATDsand services that will give badly needed coherence tothe field.This paper reflects the conviction that the develop-

ment of ATD-specific outcome models will be facilitatedby having available a framework that is potentiallyapplicable to many types of ATDs. The frameworkcan assist model developers in choosing the assumptionson which to base device-specific outcome models, select-ing the variables to include in them, and in designating

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the user populations to which they apply. The frame-work also may contribute to developing an ATDoutcomes research agenda by highlighting measures thatneed to be developed and by identifying testable hypoth-eses concerning, for example, dissatisfaction withdevices or their discontinued use.

The assumptions underlying the framework arepresented first, followed by its detailed description.The paper concludes with a discussion of some of theframework’s implications for the field of research onATD outcomes.

Assumptions underlying the framework

As abstractions drawn from complex realities,conceptual frameworks may initially be products ofunstated intuition. Converting as much of that tacitunderstanding as possible into explicitly stated assump-tions can enhance their utility and assessment. Amongthe assumptions underlying the present framework arethe following:

(1) Progress in ATD outcomes research can beaccelerated by developing an overarching frame-work that can serve as a template for causalmodels that are specific to given types of devices.The net result will be models that have theframework as their mantle and device-specificconsiderations as their core.

(2) Device use should be viewed in a developmental(time-dependent) framework.11 Two stages canbe usefully distinguished, an initial one asso-ciated with procurement of a device, and asubsequent one associated with all of the eventsthereafter—whether they span weeks, months, oryears.

(3) The full realization of the framework shouldaccommodate both objective (‘outsider’) andsubjective (‘insider’) perspectives when oper-ationalizing the variables being considered,so long as they make measurable contributionsto ATD outcomes. The principal subjectiveperspective is, of course, that of the indivi-dual ATD user. The difference can be clarifiedby considering the outcome, ‘Walking 50 feeton a smooth surface’. An objective approachmight entail a video recording of thatattempted performance. A subjective approachmight be based on asking the individual, ‘Howmuch difficulty do you have walking 50 feeton a smooth surface?’ The response choicescould include ‘Can’t do it at all’ at one

extreme, and ‘No difficulty whatsoever’ at theother.

(4) The framework should also provide for multiplestakeholders’ views of ATD outcomes, as long asthey affect the value attributed to differentoutcomes. Included are the perspectives ofindividuals comprising users’ personal networks(e.g., family members, friends, and co-workers),ATD service providers, manufacturers, vendors,payers, researchers, and policy analysts.

(5) Preference should be given to incorporating intothe framework applicable concepts and termi-nology that are the products of systematicdeliberation in related contexts. Prime examplesare several of the domains comprising theInternational Classification of Functioning, Dis-ability and Health (ICF).12

(6) Among the ‘Personal Factors’12 to be highlightedare those that depict users as being active andgoal-oriented, and not merely as passive recipi-ents of services. The constructs of personalcontrol and self-efficacy are particularly appro-priate in that regard. Emphasizing the role ofusers’ personal goals assures a conceptual homefor approaches to ATD services that accentuatethe active involvement of consumers, e.g., theAssistive Technology Device Predisposition As-sessment,13 and helps ensure that they are asrigorously researched as other components ofthe framework.

(7) In principle, ATD outcomes encompass anychanges in users’ lives or their environment thatare causally attributable to use of a device. Thatlatitude permits the possibility of finding somechanges that were unintended by either providersor device recipients. However, practical consid-erations dictate that investigators choose rela-tively few outcomes to assess from the myriadpossible ones. For most purposes, the highestpriority should be assigned to measuring out-comes that relate to individual users’ needs andobjectives in obtaining devices.13, 14

(8) Influences on ATD outcomes should be distin-guished according to their hypothesized functionas mediating or moderating factors. Mediatingfactors are involved in transmitting causalinfluences from one set of events (antecedents)to others (consequences).15 In other words, theyaccount in part for the consequences. The criticalantecedent in the framework being presented isprocurement of a specific type of ATD. Keymediating events are the introductory and longer-

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term use of that device-type. Some events serveas both outcomes and mediators, longer-term usebeing an example.

Moderating factors, whether categorical (e.g.,gender) or continuous (e.g., age), are ones thataffect the direction and/or strength of therelationship between antecedent variables andtheir consequences. They do not play a causalrole, per se, in producing those consequences.Moderating co-factors in the present frameworkinclude, for example, device users’ comorbiditiesand the concurrent interventions they may beundergoing.

Both moderating and mediating factors canbe distinguished in terms of ones that lendthemselves to being changed by interventionand those that do not. For example, moderat-ing factors such as individuals’ self-efficacyand social support are susceptible to interven-tion; age and marital status are not. Accord-ingly, the framework may help to identifyopportunities for intervening, either directly orindirectly, in order to optimize ATD out-comes.

(9) Endpoints for the modelling framework areeither continued use of a device in the longer

term or discontinuation of its use. The frame-work can be of value in highlighting the myriadinfluences that need to be considered andweighed, one against the other, in predictingthose mutually exclusive endpoints.

The conceptual framework

The conception being presented is an adaptation of aschema that is frequently found in the health sciencesliterature. Outcomes are viewed as resulting from aninteraction among characteristics of an intervention,the recipients of that intervention, and their environ-ment.The principal directions of causal influences are

denoted in figure 1 by solid lines with arrows. Procure-ment of device-type comprises the precipitating eventfor the mediating processes and outcomes that follow.Three considerations are entailed in device procurement,(1) needs for a device, (2) the type of device, consideringboth its intrinsic and extrinsic properties, and (3) theservices that may be involved.Needs for an ATD can be considered from candidate-

users’ perspectives on the functional deficits they wish tooffset or from device providers’ perspectives on thatissue. Individualized profiles of needs constitute bench-

Figure 1 A framework for modelling the outcomes of assistive technology devices.

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marks against which the outcomes of device procure-ment can be gauged. The consideration of needs alsoencompasses individuals who, personal needs notwith-standing, do not secure a device, a lack of financialresources being one possible reason. They constitute apotentially important comparison group against whichthe outcomes of device-enabled individuals can becontrasted.

The qualifying term, ‘type’, in the label for the frame-work’s beginning-point denotes the interest of modellersin categories of devices, rather than in concrete devicesconsidered one at a time. That underscores the needfor a taxonomy of ATDs that distinguishes amongthem, based on their intended impacts on users’ func-tioning.

The intrinsic properties of device-types includefeatures of their physical design and operating perfor-mance that impact on specific aspects of users’ function-ing. The reliability of devices is a key feature of theiroperating performance that is likely to affect users’ func-tioning. The extrinsic properties of devices include theircosts, availability, and operating condition. The latter’sinclusion reflects the fact that poorly maintained, barelyfunctioning devices are not likely to produce the sameoutcomes as well-functioning ones, nor are they likelyto foster users’ satisfaction with them.

The services associated with procurement of a devicevary considerably in their complexity. In a relativelysimple instance, an individual learns about a devicefrom a friend and proceeds to obtain it from a vendorthrough the Internet. Services are much more multifa-ceted if provided in the context of a rehabilitationprogramme. Key to those services is assessment ofcandidate users’ functional goals; their capabilitiesand limitations, both physically and cognitively; andcharacteristics of the environments in which assistanceis needed.16 Other services may involve advice on alter-native device solutions, identification of sponsorshipsources, transactions with a vendor, and possible modi-fication of a device to accord more with the individualuser’s needs.

In summary, device procurement is a complex consid-eration that needs to be modelled in its own right.

From the standpoint of the modelling framework,outcomes are not produced by devices per se, but ratherby the manner and amount of their use. The latter canbe quantified in terms of usage frequency (e.g., numberof times per week) and duration (e.g., number of hoursper day). Manner of usage refers to the circumstances inthe user’s life in which the device is used and to theappropriateness of that usage, i.e., the extent to whichthe device is used within the operating conditions that

are specified for it. For example, a lightweight wheel-chair designed for hospital use is not employed appro-priately if it is used for shopping and active recreation.

Similar to other aspects of the framework, the periodof introductory use can be understood differently,depending on whose vantage point is considered. Froma user’s standpoint, it may be the period of time neededto become comfortable with using a device in relevantenvironments. From a provider’s standpoint, it may bethe time needed during an initial trial for the consumerto become capable of using a device effectively andsafely according to the recommendations for it. Regard-less of the perspective, the period of introductory useapplies to all ATDs and all users, though its natureand duration vary a great deal depending on the particu-larities of each.

Introductory use results in an array of shorter-termoutcomes, devices’ effectiveness being one of them. Asunderstood in this framework, it embraces the Activitiesand Participation domain of the ICF.12 Various device-specific models will address different subcategories ofActivities and Participation, e.g., Communication, Mobi-lity, or Self-Care, depending on the intended functionalimpacts of the devices being considered.

A device’s efficiency is another way of consideringits shorter-term outcomes. It extends the concept ofeffectiveness by taking into account the resources thatare used in producing the observed effects. In thismanner, costs are introduced into the estimation ofoutcomes.17 (As indicated below, costs also serve asa Moderating Co-Factor.) Another shorter-termoutcome is device satisfaction. Adapting a definitionoffered by Hulin,18 it is definable as users’ cognitive,affective, and evaluative responses (on a like-dislikedimension) to the perceived characteristics of devicesand their impacts. It may be noted that the threeoutcomes, effectiveness, efficiency, and device satisfac-tion, are the key components of ‘device usability’, aconcept promulgated by the International Organiza-tion for Standardization.19

The other two shorter-term outcomes are psychologicalfunctioning and subjective well-being. The latter refers tothe degree to which people have positive appraisals andfeelings about their lives, considered altogether or interms of particular domains, e.g., health and recrea-tion.20 Device use may affect all three principal featuresof psychological functioning, conation, affect, and cogni-tion. Recent studies particularly highlight effects onusers’ feelings of competence and efficacy, adaptability,and self-esteem.21, 22

The shorter-term outcomes result from an interactionbetween introductory use and a host of moderating co-

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factors. The latter include the ICF domains of BodyFunctions, Body Structure, Activities and Participation,Environmental Factors, and Personal Factors. Othermoderating co-factors are concurrent interventions, e.g.,on-going physical therapy or speech therapy, continuingATD services, comorbidities, and costs. These categoriesare all quite broad and contain many sub-factors. Thespecific ones that are chosen will depend on particularuser populations and the types of devices beingmodelled.

Devices will continue to be used, underutilized, orentirely set aside depending on the extent to which theyhave been effective, efficient, and a source of satisfactionand enhanced well-being. Thus, assuming the role ofmediating variables, those shorter-term outcomes resultin longer-term use or discontinued use. (An intermediateamount of usage that might be labelled ‘intermittent-’ or‘inconsistent-use’ is readily imaginable as well.) Forsome individuals, discontinued use of a device may serveto re-initiate the previous sequence, beginning withprocurement of another device or a different kind ofsupport altogether.

Longer-term use interacts with the specified moderat-ing co-factors to produce a variety of longer-termoutcomes. As an encompassing array of ATD outcomedomains, their composition is identical with that of theshorter-term outcomes. However, the two may takedifferent forms in causal models of specific devices.For example, domains such as Effectiveness and Effi-ciency may be more salient in the shorter term thanare Psychological Functioning and Subjective Well-being,but the reverse may be true in the longer term. Alterna-tively, specific outcomes within the same general domainmay take on new importance in the longer term as users’goals evolve and their environments change.

The moderating co-factors that act in the longer termare the same that were in play earlier, though their speci-fic features may differ as well. For example, continuingATD services may increasingly take the form of repairservices and product upgrades as the duration of usageincreases. Interaction of the longer-term outcomes andthe moderating co-factors results in either continued ordiscontinued use that in turn may result in repetition ofthe preceding sequence.

Though not represented in the figure, two otherfeatures of the framework are considered to be essential.The first is allowing both a subjective perspective (that ofusers themselves) and an objective perspective on opera-tionalizing most of the variables that constitute theframework’s outcomes and moderating co-factors. Thesecond is the differentiation of multiple stakeholderperspectives including those of users’ family members,

friends, and co-workers, ATD service providers, manu-facturers, vendors, payers, researchers, and policyanalysts. Particular ATD-specific models need not makeprovision for all of those perspectives, but their develo-pers need to be explicit about which perspectives wereadopted in selecting variables and in operationalizingthem.

Discussion

The framework being described does not purport tobe a model of ATD outcomes. Instead, it is intendedto be a conceptual structure within which to developsuch models. The models themselves are expected tofocus on specific device-types. The models will specify:(1) the functional problems upon which the device-type is intended to impact; (2) critical features of thedevice-type that are putatively responsible for thoseimpacts; (3) characteristics of individuals that makethem candidates for being successful users; (4)elements and contingencies in the causal chainconnecting procurement of the device-type with likelyoutcomes; and (5) expected changes in users’ statusand in their environment that constitute thoseoutcomes, both near- and long-term. The frameworkis intended to facilitate the development of suchmodels by identifying the principal domains fromwhich variables can be chosen, the definitions of somekey variables, the junctures in the causal flow at whichmoderating variables are likely to have effects, and thesequencing of some of the principal influences onoutcomes.The development of device-specific models is likely

to be motivated by utilitarian, clinical concerns suchas comparing the outcomes of competing devices ofdifferent but related types. The fact that the modelswill concern particular device-types, user populations,and conditions of device use will facilitate their devel-opment. Models represent hypotheses, and as such,their developers will be able to draw on their personalknowledge of the target-devices, the reported experi-ence of users and providers, as well as on any researchfindings that are available. That aggregate experienceshould aid in creating models that fulfil the goalsfor them, namely, identifying mediating processes,predicting specific outcomes, and explaining why thoseoutcomes are expected.An emphasis on device-specific models need not be at

the expense of developing broader conceptual models ofATD outcomes that apply to multiple device-types andusers. An evolutionary process is envisioned in whichthe availability of numerous device-specific models sets

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the stage for the emergence of more general ones. To alarge extent, they will be based on features shared bythe device-specific models. The result will be a hierarchythat has a variety of device-specific models comprisingits foundation, and a few broadly conceived modelsforming its higher levels.

The framework encompasses outcomes that rangefrom changes in restricted aspects of users’ Body Func-tions to far-ranging influences on their Activities andParticipation, psychological functioning, and subjectivewell-being. The precise causal pathways that lead tothose outcomes remain to be modelled and empiricallyvalidated. Some psychological or social outcomes mayreflect the cascading effects of ATDs’ initial impactson delimited aspects of users’ Body Functions. Thus,even modest enhancement of a single sensory modalitysuch as hearing may ultimately improve functioning innumerous social roles. Distinct repercussions onpsychological functioning may occur as well, e.g., onindividuals’ sense of control over their lives.22 Alterna-tively, certain kinds of devices may directly affectusers’ Activities and Participation or their psychologicalfunctioning, independently of their effects on BodyFunctions. For example, a minor improvement in thecosmetic appearance of a hearing aide may signifi-cantly improve user acceptance, leading to increaseduse and subjective well-being, without enhancing audi-tion at all.

The framework identifies a diversity of factors thatmay influence the outcomes of devices and services.Many of the factors designated as moderating co-factorsare cited in the Matching Person and TechnologyModel,13 an effort to systematize the process of matchingcandidate users and devices. It identifies numerousfeatures of individuals and their environment thatrequire consideration as potential moderators. A similarmix of physical, social, psychological, and environmen-tal variables has been cited by investigators concernedwith identifying the reasons why the use of devices isdiscontinued.16, 23 The framework may help to advanceknowledge about such disuse by promoting the develop-ment of conceptual models that organize availableresearch findings and that point to the knowledge gapsthat remain.

The choice to distinguish two stages of usage,introductory use and longer-term use, is based on apair of key notions. The first is that adaptation toATDs is an inherently time-dependent process thatentails not only skill acquisition, but for manydevices, emotional accommodation as well.24, 25

Consistent with extensions of adaptation theory,26, 27

adaptation to devices is feedback-dependent and thus

is understandable as being a learning or career devel-opment process. That process continues to evolve asindividuals habituate to the novelty of a newlyacquired device and as they encounter new situationsand settings that challenge how they use it and howthey feel about it.28 Altered usage patterns may bedictated as well by changes in individuals’ functionalcapabilities over time,11 or by deterioration in thedevices’ performance.

Distinguishing periods of introductory use and longer-term use is important, too, in view of the distinctiveissues that are confronted by novice users of ATDs.They include (1) coming to terms with functional lossesand the need for a device, and (2) concluding that it willbe useful to them, not only in their current setting, e.g., arehabilitation hospital, but also in their future lifeoutside of the hospital. Testifying to the import of theintroductory period, devices are more likely to continuebeing used if, during hospitalization, neophyte usershave a positive attitude toward them and expect to usethem upon returning home.23

From an outcomes perspective, ATD use, bothintroductory and long-term, is a complex, multivariateconstruct. Two of its features, the relative frequencyof a device’s use and the duration of that usage, arereadily quantified. Quantifying a device’s conditionsof usage, i.e., the circumstances in the user’s life inwhich it is used, is somewhat more of a challenge.Harder still is operationalizing judgments about theappropriateness of that usage. ‘Appropriateness’ refersto the extent that a device is being used within theoperating conditions that are specified for it. A hear-ing aid that is frequently operated on depletedbatteries or a powered wheelchair that is used in citystreets is not being used appropriately. They are likelyto produce different outcomes than identical devicesthat are being used in accord with the operatingconditions set down for them.

Some of the framework’s components are simplyplaceholders for elaborations that need to be suppliedby device-specific models. Other components areworked-out in considerable detail, thanks to the strategyof incorporating taxonomies that are already highlyelaborated. The various ICF constructs and their asso-ciated classifications are a case in point. They will hope-fully prompt ATD outcomes researchers to explore therole of heretofore-neglected variables, those pertainingto users’ environment being prime examples. In thatconnection, Lenker and Jutai29 have provided an analy-sis that, among other things, identifies examples ofATDs that can facilitate functional performance in eachof the ICF domains, and that highlights available

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measures that are domain-specific or applicable acrossdomains.

Procurement of a device-type will also require elabora-tion in ATD-specific models. Substantially more isentailed than simply naming the kind of device. Servicesthat enable people to access devices and use them effec-tively need to be identified, as do the design features ofdevices that account for purported user-benefits. Ifcarried out adequately, the characterization of devicesand services will facilitate the replication of studies,provide a basis for assessing whether the actualities ofdevice procurement and usage conformed to intendedpractices, and assist in interpreting the findings ofoutcome studies.

Though not represented in the graphic representationof the framework, expressed provision is made fordistinguishing the subjective perspective of users froman objective perspective. For example, Socializing, acomponent of Activities and Participation in the ICF,12

can be assessed objectively by counting the number oftimes each week that an ATD user engages in informalgatherings with others. It can be assessed subjectivelyby asking the user whether she/he feels limited in, orsatisfied with, such engagements. Conjunction of theinsider/outsider distinction with the specified outcomedomains that are specified in the framework providesdistinct conceptual niches for more recently developedmeasures of ATD outcomes, e.g., the PsychosocialImpact of Assistive Devices Scale30, 31 and the QuebecUser Evaluation of Satisfaction with AT.32

Among the objective perspectives that may be takenon ATD outcomes are those of various stakeholdersthat include users’ family members and co-workers,ATD service providers, manufacturers, vendors, spon-sors, researchers, and policy analysts. They may verywell differ in the importance that is attributed tovarious outcomes. For example, manufacturers andvendors may stress users’ device satisfaction, sponsorsmay emphasize the minimization of costs, and policyanalysts may place greatest importance on societalbenefits such as Work and employment. Validatingsuch common-sense expectations is a task for futureresearch. If confirmed, new outcome instrumentsmay have to be developed that represent the moredistinctive stakeholder perspectives. Systematic meth-ods may have to be devised as well for assigningdifferential weights to the outcome variables used inparticular studies. At the same time, the frameworkcan be used to encourage research that promotes acommon understanding among stakeholders on thelegitimacy of various perspectives in consideringATD outcomes.

Acknowledgements

Funding was provided in part by grant H133A010401 from the

National Institute on Disability and Rehabilitation Research. The

authors are all members of the Consortium on Assistive Technology

Outcomes Research (CATOR).33

References

1 Gitlin LN. Assistive technology in the home and community forolder people: psychological and social considerations. In: MJScherer (ed) Assistive Technology: Matching Device and Consumerfor Successful Rehabilitation. Washington, DC: American Psycho-logical Association, 2002; 109 – 122.

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