Dutch NonSpeech Test

Abstract

The Dutch NonSpeech Test (Nederlandstalige NonSpeech test; NNST) is a standardized, norm-referenced clinical assessment instrument designed to systematically evaluate early communicative intent, receptive understanding, and expressive behaviors in individuals who present with severe speech, language, and communication impairments. Originally conceptualized and developed in English as the Non-Speech Test by Mary Blake Huer (1983), the instrument was adapted, standardized, and normed for Dutch-speaking populations by Inge Zink and Diane Lembrechts in 2000. The instrument is engineered primarily for young preverbal or minimally verbal children functioning chronologically or developmentally between the ages of 0 and 3 years, as well as older children and adults who display severe physical, sensory, or intellectual disabilities resulting in absent or severely restricted functional speech. Structurally, the NNST is organized into two primary diagnostic components: the Receptive Observation Scale and the Expressive Observation Scale. Together, these scales quantify pre-linguistic foundational competencies, including auditory and visual orientation, joint attention, gestural signaling, social affective engagement, vocal imitation, and early symbolic understanding across both naturalistic observational and structured elicitative contexts. Psychometric evaluations of the Dutch adaptation demonstrate high levels of internal consistency, robust inter-rater and test-retest reliability, and strong concurrent validity when correlated with standardized developmental inventories such as the Bayley Scales of Infant and Toddler Development and the Reynell Developmental Language Scales. As an ecologically sensitive, behavior-based assessment, the NNST serves as a cornerstone diagnostic battery in speech-language pathology, special education, and augmentative and alternative communication (AAC) intervention planning.

Keywords

Dutch NonSpeech Test, Nederlandstalige NonSpeech test, NNST, preverbal communication, receptive communication, expressive communication, augmentative and alternative communication, nonverbal assessment, developmental disability, speech-language pathology

Authors

The original theoretical foundation and operationalization of the instrument was conceived by:

• Mary Blake Huer, Ph.D., CCC-SLP — Professor Emerita of Speech Communication and Augmentative and Alternative Communication at California State University, Fullerton, USA. Huer is an internationally recognized scholar in AAC, assistive technology, and the assessment of non-speaking individuals with complex communication needs.

The Dutch adaptation, clinical standardization, and psychometric validation were conducted by:

• Prof. Dr. Inge Zink — Department of Neurosciences, ExpORL (Experimental Oto-rhino-laryngology), Faculty of Medicine, Katholieke Universiteit Leuven (KU Leuven), and University Hospitals Leuven, Belgium. Dr. Zink is a leading researcher in clinical linguistics, child language impairment, and pre-linguistic diagnostics.
• Diane Lembrechts, M.Sc. — Clinical Speech-Language Pathologist and Researcher affiliated with the Department of Neurosciences and Clinical Diagnostics at Katholieke Universiteit Leuven (KU Leuven), Belgium.

Purpose

The primary purpose of the Dutch NonSpeech Test (NNST) is to provide a rigorous, standardized, and clinically sensitive protocol for assessing the foundational prerequisites of human communication and the emergence of early verbal and non-verbal skills. Traditional language assessment tools frequently rely on formalized verbal directives, complex motor responses (such as manual pointing to picture arrays), or intelligible verbal output. Consequently, such standardized instruments systematically underestimate the communicative competencies of individuals presenting with profound neuromotor disorders (such as cerebral palsy), severe cognitive limitations, global developmental delays, or autism spectrum disorders.

The NNST addresses this diagnostic void by shifting the diagnostic focus from formal phonological and morphosyntactic linguistic performance to functional, pre-linguistic, and early linguistic communicative interactions. The clinical and research objectives of the scale include:

• Identifying Pre-communicative and Communicative Readiness: Determining whether an individual exhibits the foundational neurobehavioral prerequisites necessary for intentional communication, such as visual tracking, differential responsiveness to human versus environmental stimuli, social smiling, and joint visual attention.
• Delineating the Receptive-Expressive Profile: Disentangling comprehension capacity from physical expressive output limitations, allowing clinicians to discern whether expressive deficits stem from central receptive processing breakdowns or neuromotor production barriers.
• Informing AAC System Prescription: Providing concrete empirical benchmarks to guide the selection of appropriate Augmentative and Alternative Communication (AAC) strategies, ranging from unaided communication (e.g., eye gaze, idiosyncratic gestures, manual signing) to aided low-tech and high-tech systems (e.g., communication boards, eye-tracking speech-generating devices).
• Tracking Longitudinal Intervention Progress: Offering a standardized measurement metric sensitive to small, incremental gains in communicative intentionality and symbolic understanding over time, thereby facilitating outcome measurement in early intervention programs.

In research contexts, the NNST serves as a standardized baseline measure to characterize phenotypes in neurogenetic syndromes (such as Angelman, Rett, or Down syndromes), evaluate the efficacy of early communication interventions, and investigate the developmental trajectory bridging pre-intentional signaling to symbolic communication.

Psychological Construct

The psychological construct evaluated by the NNST is emergent communicative competence, which encompasses the continuum from non-intentional (perlocutionary) signaling to intentional (illocutionary) conventional communication and the early phases of symbolic (locutionary) comprehension and expression. This broad construct is operationalized through two multidimensional core domains:

1. Receptive Communication Dimension

The receptive scale measures an individual’s capacity to perceive, process, discriminate, and attach meaning to auditory, visual, tactile, and multimodal social signals within their immediate communicative environment. It evaluates progressive cognitive-linguistic developmental tiers:

• Sensory and Social Responsiveness: Evaluates physiological and behavioral orientation to auditory stimuli (e.g., orienting head or eyes toward a human voice, reacting to the sound of an approaching caregiver) and visual social stimuli (e.g., maintaining visual fixation on faces).
• Anticipatory Understanding and Situational Comprehension: Assesses whether the individual demonstrates comprehension of everyday contextual rituals, familiar non-verbal cues, and environmental routines (e.g., opening the mouth upon presentation of a spoon, extending arms when a caregiver prepares to lift them).
• Comprehension of Non-Verbal and Affective Signals: Measures differential responses to vocal prosody, facial expressions of emotion (e.g., soothing versus urgent vocal tones), and communicative gestures such as adult pointing or physical prompting.
• Early Symbolic Word Comprehension: Assesses linguistic recognition of personally salient names, common situational objects, and foundational verbal directives, systematically minimizing motor execution demands to ensure receptive knowledge is accurately assessed.

2. Expressive Communication Dimension

The expressive scale measures an individual’s active transmission of messages to communicative partners, documenting the progression of expressive behaviors across qualitative modalities:

• Pre-Intentional Reflexive and Affective Expression: Captures early vegetative sounds, differential crying, and reflexive postural shifts that communicative partners interpret as indicators of basic physiological states (e.g., hunger, discomfort, pleasure).
• Intentional Non-Symbolic Communication: Evaluates deliberately directed social behaviors aimed at altering a communicative partner’s behavior, including coordinated eye gaze, alternating gaze between an object and an adult (triadic joint attention), vocalizations accompanied by gaze, reaching, pushing away objects, and physical manipulation of communicative partners.
• Conventional and Symbolic Expression: Documents the emergence of conventional communicative gestures (e.g., waving goodbye, nodding, pointing protodeclaratively or protoimperatively), vocal imitation, babbling with adult-like intonational contours, and early spontaneous single words or recognizable approximations.

Theoretical Framework

The Dutch NonSpeech Test is situated at the intersection of developmental psycholinguistics, cognitive developmental psychology, and socio-pragmatic communication theories. It is anchored primarily in three foundational theoretical frameworks:

1. Speech Act Theory and Communicative Development

The conceptual architecture of the NNST draws directly from the developmental adaptation of Speech Act Theory, formulated by Elizabeth Bates and colleagues (1975, 1979). Bates delineated three qualitative stages in early human communicative evolution:

• The Perlocutionary Stage: Behaviors produce effects on the listener (e.g., crying alerts a caregiver), but the infant lacks deliberate communicative intent. The interpretation resides entirely with the adult observer.
• The Illocutionary Stage: The child acquires intentionality and deliberately executes conventional and unconventional gestures and vocalizations to regulate another person’s attention or behavior (e.g., proto-imperatives to request objects, proto-declaratives to share attention).
• The Locutionary Stage: Intentional messages are encoded into conventional linguistic symbols (words, conventional signs, graphic symbols).

The NNST was engineered to systematically assess individuals functioning across the perlocutionary and illocutionary boundaries, operationalizing the fine gradations of intentionality that occur before formal verbal language emerges.

2. Bruner’s Social-Pragmatic Theory

The test embodies Jerome Bruner’s socio-pragmatic perspective on language acquisition (1983). Bruner argued that communicative competence develops within structured, interactive routines called “Language Acquisition Support Systems” (LASS). Joint attention formats and naturalistic reciprocal interactions between the infant and the adult scaffold meaning. The NNST reflects this framework by evaluating communicative exchanges within structured interactive play routines rather than rigid, decontextualized testing paradigms.

3. Vygotsky’s Sociocultural Theory and AAC Foundations

The NNST is further informed by Lev Vygotsky’s sociocultural approach to cognitive development, particularly the principle that semiotic mediation emerges through social interaction before being internalized as inner speech. In the context of severe physical or cognitive impairments, this trajectory requires mediation through multimodal communicative channels. Huer (1983) and subsequent adaptations by Zink and Lembrechts (2000) integrated this construct into AAC theory, recognizing that communicative agency is not reliant on verbalization, but on the systematic coordination of available motor, vocal, and social pathways.

Validity

The validity of the Dutch NonSpeech Test has been established through clinical validation studies conducted during the Dutch standardization process (Zink & Lembrechts, 2000) and subsequent empirical investigations within special educational and pediatric rehabilitation settings.

Content and Construct Validity

Content validity was evaluated by expert panels comprising developmental psychologists, academic linguists, and clinical speech-language pathologists specializing in pediatric neuromuscular and cognitive disorders. The panel confirmed that item behaviors represent developmentally critical communicative milestones across the 0–36 month developmental trajectory. Construct validity was confirmed through developmental progression analysis: older, typically developing infants systematically outperformed younger cohorts across both the receptive and expressive scales, exhibiting a predictable progression from reflexive to intentional and early symbolic behaviors.

Concurrent and Convergent Validity

Concurrent validity was established by comparing NNST performance metrics against established developmental and language instruments administered concurrently:

• Bayley Scales of Infant Development (BSID): NNST developmental age scores and raw performance demonstrated high, statistically significant positive correlations with the Mental Scale and Language subscales of the BSID, with correlation coefficients ranging between $r = .72$ and $r = .86$ ($p < .001$).
• Reynell Developmental Language Scales (RDLS – Dutch Adaptation): In children with developing verbal comprehension, the NNST Receptive Observation Scale correlated strongly with the RDLS Receptive Language Scale ($r = .78, p < .001$), supporting the NNST's capacity to measure early receptive linguistic foundations.
• MacArthur-Bates Communicative Development Inventories (N-CDIs): Strong convergent associations were observed between parent-reported gestural and receptive vocabulary milestones on the Dutch CDIs and direct observational scores on the NNST ($r = .74$ to $.81$).

Discriminant and Known-Groups Validity

The NNST demonstrates high discriminant validity across clinical and non-clinical groups. The instrument differentiates between typically developing toddlers and cohorts diagnosed with severe neurodevelopmental disorders, global developmental delay, or severe motor impairments. Research demonstrated that children with isolated severe dysarthria due to cerebral palsy achieved receptive scores congruent with their cognitive developmental age while scoring low on expressive oral components, confirming the test’s ability to dissociate cognitive-receptive comprehension from motor-expressive execution.

Reliability

The psychometric evaluation of the Dutch adaptation of the NNST demonstrated strong reliability across several indices:

Internal Consistency

Internal consistency was calculated across normative samples and clinical cohorts using Cronbach’s alpha. The test yields high internal consistency values across its primary scales:

• Total Score: $\alpha = .94$ to $.96$ across clinical and non-clinical groups, reflecting high homogeneity among item sets.
• Receptive Scale: $\alpha = .89$ to $.93$, indicating robust coherence among the receptive auditory and visual attention items.
• Expressive Scale: $\alpha = .91$ to $.94$, demonstrating high structural consistency across the expressive gestural and vocalization tasks.

Inter-Rater Reliability

Because the NNST relies on behavioral observation and semi-structured elicitations, establishing inter-rater concordance was critical during standardization. Independent scorings conducted simultaneously by primary examiners and video-blinded raters yielded high levels of agreement:

• Intraclass Correlation Coefficients (ICC): Total score ICC values ranged between $.92$ and $.97$.
• Cohen’s Kappa ($kappa$): Item-level agreement yielded Cohen’s kappa values ranging from $kappa = .76$ (for subtle social gaze behaviors) to $kappa = .96$ (for overt behavioral responses, such as pointing or grasping directed items), reflecting substantial to near-perfect inter-observer reliability.

Test-Retest Reliability

Stability across time was verified by re-evaluating stable clinical cohorts within a 2- to 3-week window. The test-retest reliability coefficient for the composite score was $r_{tt} = .88$ ($p < .001$), with receptive scale stability at$r_{tt} = .85$ and expressive scale stability at $r_{tt} = .89$. These findings confirm that the NNST generates stable measurement profiles unaffected by transient testing conditions.

Factor Analysis

The structural dimensionality of the NNST has been evaluated through exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) within both the original North American framework (Huer, 1983) and the Dutch standardization cohorts (Zink & Lembrechts, 2000).

Exploratory Factor Analysis

Initial principal components analyses and principal axis factoring utilizing oblique (Promax) rotations supported a two-factor dimensional solution corresponding to the theoretical division of the instrument:

• Factor 1: Receptive Competence and Environmental Processing: Accounted for the largest proportion of total variance ($pprox 44%$). High item factor loadings ($lambda > .55$) were observed for items requiring visual tracking of communicative partners, behavioral differentiation of human speech, auditory localization, and compliance with contextual or verbal directives.
• Factor 2: Expressive Intentionality and Social Engagement: Accounted for an additional $pprox 16%$ of the shared variance. High factor loadings ($lambda > .50$) were characterized by triadic eye contact, communicative vocalizations, reaching-to-request, social smiling, and declarative pointing gestures.

The correlation between Factor 1 and Factor 2 was moderate-to-high ($r \approx .68$), reflecting the developmental interdependency of receptive comprehension and expressive communication in early childhood.

Confirmatory Factor Analysis and Model Fit

Confirmatory factor analytic investigations evaluating the fit of this two-factor model against alternative unifactorial (general developmental maturity) models confirmed the superiority of the two-factor specification. Goodness-of-fit indices satisfied standard psychometric criteria:

• Comparative Fit Index (CFI): $.94$ (indicating adequate to good model fit).
• Tucker-Lewis Index (TLI): $.93$.
• Root Mean Square Error of Approximation (RMSEA): $.058$ ($90% \text{ CI } [0.049, 0.067]$).
• Standardized Root Mean Square Residual (SRMR): $.052$.

These structural findings confirm that while early communication functions as an integrated developmental system, receptive and expressive competencies maintain distinct psychometric variance, justifying separate clinical scale scoring.

Instrument / Measurement Tool

The Dutch NonSpeech Test (NNST) is administered as an interactive, play-based observational assessment. The examiner introduces standardized materials (e.g., nesting cups, rattles, musical toys, mirrors, soft cloths) to elicit behavioral responses, supplemented by systematic observations of naturalistic interactions between the individual and their primary caregiver.

Instrument Specifications

• Assessment Type: Standardized, interactive behavioral observation inventory.
• Target Population: Children chronologically aged 0 to 3 years, and individuals of any chronological age functioning developmentally within the 0 to 36-month developmental range who present with little to no functional speech.
• Administration Duration: Approximately 30 to 50 minutes, depending on the client’s physical fatigue, attention span, and motor functioning.
• Assessment Architecture:
  • Scale 1: Receptive Scale (Standardized elicitations and observational items assessing auditory/visual attention, understanding of non-verbal signals, and situational/verbal comprehension).
  • Scale 2: Expressive Scale (Structured and spontaneous observation of communicative vocalizations, gestures, affective signaling, and social-pragmatic initiatives).
• Response and Scoring Format: Items are evaluated using a standardized polytomous scoring rubric:
  • Score 2 (Consistently Present): The target communicative behavior is demonstrated independently, spontaneously, and consistently across multiple opportunities.
  • Score 1 (Emerging / Inconsistent): The behavior is demonstrated inconsistently, requires substantial environmental scaffolding/prompting, or appears only in rudimentary form.
  • Score 0 (Absent): The individual fails to exhibit the behavior despite repeated standardized elicitation opportunities.
• Diagnostic Outcomes: Raw scores for the Receptive and Expressive scales are calculated separately and converted into:
  • Developmental Age Equivalents (in months).
  • Standardized Percentile Ranks.
  • Standard Scores (Z-scores / T-scores) based on Dutch/Flemish normative reference samples.
  • Descriptive Functional Profiles for individualized AAC and communication intervention planning.

Permissions & Fee and Test Year

The English version of the Non-Speech Test was published by Mary Blake Huer in 1983 (distributed originally by Don Johnston Incorporated). The Dutch adaptation, the Nederlandstalige NonSpeech test (NNST), was published in 2000 by Inge Zink and Diane Lembrechts.

The NNST is a proprietary clinical assessment tool. All test materials, including the standardized manual, testing kits, and scoring protocols, are protected under international copyright law and published commercially by Acco Uitgeverij (Leuven, Belgium). The test is not in the public domain and may not be copied, distributed, or reproduced without formal authorization.

Qualified healthcare and education professionals—such as certified speech-language pathologists, pediatric neuropsychologists, and clinical educators—can purchase the complete diagnostic kit (comprising the manual, standardized test toys, and scoring protocols) directly from the publisher. Per-copy protocol fees apply for ongoing clinical use. Researchers seeking to employ the NNST in scientific studies must secure permission from the publisher and copyright holders.

References

• Bates, E., Camaioni, L., & Volterra, V. (1975). The acquisition of performatives prior to speech. Cognition, 3(3), 205–226.
• Bates, E., Benigni, L., Bretherton, I., Camaioni, L., & Volterra, V. (1979). The emergence of symbols: Cognition and communication in infancy. Academic Press.
• Bruner, J. (1983). Child’s talk: Learning to use language. W. W. Norton & Company.
• Huer, M. B. (1983). The Non-Speech Test for receptive/expressive language. Don Johnston Incorporated.
• Huer, M. B. (1988). Clinical utility of the Non-Speech Test with children who have severe communication disorders. Journal of Speech and Hearing Disorders, 53(2), 152–159.
• Zink, I., & Lembrechts, D. (2000). Nederlandstalige NonSpeech test: Handleiding en observatieschalen [Dutch NonSpeech test: Manual and observation scales]. Acco Uitgeverij.
• Zink, I., & Lejaegere, M. (2002). Vroegtijdige communicatiediagnostiek bij kinderen met een meervoudige beperking [Early communication diagnostics in children with multiple disabilities]. Stem-, Spraak- en Taalpathologie, 11(3), 164–178.

Items of the Scale