Precursors in Communication

1. Abstract

The Precursors in Communication (known natively in Dutch as Voorlopers in Communicatie, abbreviated as ComVoor and updated as ComVoor-2; Verpoorten, Noens, & van Berckelaer-Onnes, 2004, 2016) is an internationally recognized, criterion-referenced, performance-based clinical assessment instrument designed to assess nonverbal and preverbal meaning-making (semiotics) and communicative precursors. Developed specifically for individuals experiencing severe expressive and receptive communication impairments—most notably non-speaking or minimally verbal children and adults with autism spectrum disorder (ASD), intellectual disabilities, and complex sensory impairments—the ComVoor provides action-oriented, intervention-directed indications for augmentative and alternative communication (AAC). The instrument evaluates two fundamental clinical questions: (1) what type of communicative medium or representational vehicle (e.g., three-dimensional objects, miniature replicas, color photographs, stylized pictograms, or printed graphic symbols) is psychologically meaningful to the individual, and (2) at what cognitive level of signification or meaning-making (presentation versus representation) can these communicative media be effectively implemented in daily living routines, educational environments, and structured interventions. Rather than comparing the examinee against a normative peer distribution, the ComVoor uses domain-referenced, criterion-oriented behavioral sorting tasks across two broad cognitive tiers: the Presentation Level (matching identical visual/tactile stimuli based purely on perceptual, physical attributes such as shape, color, material, and size) and the Representation Level (categorizing non-identical stimuli sharing semantic concepts, both within identical perceptual forms and across divergent perceptual forms). Psychometric evaluations of the ComVoor demonstrate exceptional internal consistency (Cronbach’s alpha > .90 across subscales), robust inter-rater agreement (Cohen’s kappa > .85), stable test-retest reliability, and strong convergent validity against standardized adaptive functioning scales, language tests, and nonverbal cognitive developmental indices. The ComVoor bridges developmental semiotics and daily clinical practice, establishing an evidence-based foundation for individualized visual support systems.

2. Keywords

ComVoor, Precursors in Communication, Voorlopers in Communicatie, augmentative and alternative communication, autism spectrum disorder, intellectual disability, semiotics, level of signification, presentation level, representation level, criterion-referenced assessment, nonverbal communication, visual schedules.

3. Authors

The instrument was conceptualized, developed, normed, and clinically standardized by leading developmental psycholinguistics and clinical neurodevelopmental specialists:

• Roger A. W. Verpoorten, Ph.D. — Clinical psychologist, psychometrician, and developmental researcher formerly affiliated with the Child Study Center and Developmental Psychopathology Department at the Leiden University, Leiden, the Netherlands. Dr. Verpoorten has specialized extensively in communicative impairments among individuals with severe-to-profound intellectual disabilities and autism.
• Ilse E. M. Noens, Ph.D. — Professor of Special Education and Clinical Child and Family Studies at KU Leuven (Katholieke Universiteit Leuven), Belgium. Dr. Noens is a prominent international scholar in neurodevelopmental conditions, focusing on early intervention, language development in ASD, and individualized communicative scaffolding.
• Ina A. van Berckelaer-Onnes, Ph.D. — Professor Emerita of Clinical Child and Adolescent Studies at Leiden University, the Netherlands. An international authority on autism spectrum conditions and severe communication disorders, she pioneered the theoretical framework linking central coherence, executive dysfunction, and semiotic development to visual communication supports.

Primary Contact & Publisher: Hogrefe Uitgevers B.V., Amsterdam, the Netherlands / Hogrefe Publishing Group. Official inquiries regarding test materials, kit distribution, and accredited user certification are managed via Hogrefe Uitgevers (hogrefe.nl).

4. Purpose

The primary clinical and diagnostic purpose of the Precursors in Communication (ComVoor / ComVoor-2) is to deliver an individualized, action-oriented profile indicating the exact visual and tactile communication modalities suitable for individuals with significant receptive and expressive communication barriers. In clinical practice, professionals working with children and adults with intellectual developmental disorders, severe autism spectrum disorder, childhood disintegrative disorders, or neurogenic communication deficits frequently encounter substantial challenges when attempting to establish visual schedules, communication boards, or assistive technologies. A widespread clinical error is the premature introduction of abstract visual symbols (such as black-and-white line drawings, Mayer-Johnson Boardmaker picture communication symbols, or complex pictorial icons) to an individual who has not yet developed the cognitive capacity for symbolic representation. Conversely, providing concrete, heavy real-world objects to an individual capable of interpreting streamlined digital icons unnecessarily restricts their communicative autonomy and environmental agility.

The ComVoor solves this clinical dilemma by empirically resolving two decisive questions:

1. Which communicative media are suitable? The test systematically evaluates the person’s functional processing across a physical hierarchy of media, ranging from tangible three-dimensional objects, functional object miniatures, and high-resolution realistic color photographs, to stylized pictograms, graphic line drawings, and written words.
2. At which level of meaning-making (signification) can these media be deployed? The test discriminates whether the examinee interprets visual stimuli at the Presentation Level (where the symbol is recognized purely through direct physical identity and perceptual matching) or at the Representation Level (where the symbol functions as a true signifier pointing to an abstract concept, class of objects, or absent referent).

Unlike conventional standardized psychometric instruments that emphasize normative percentiles or developmental quotients, the ComVoor is explicitly criterion-referenced and domain-oriented. The clinician does not evaluate whether an individual performs better or worse than a representative sample of neurotypical chronological peers. Instead, the assessment evaluates the individual’s specific cognitive-communicative profile—identifying strengths (what tasks the examinee executes fluently and independently) and operational limits (where meaning-making breaks down or shifts into perseverative, perceptual error patterns). This yields direct prescriptive recommendations for daily environments, including structured TEACCH-based physical schedules, choice boards, task organization strips, and expressive symbol systems across educational, residential, and vocational care settings.

5. Psychological Construct

The overarching psychological construct assessed by the ComVoor is levels of meaning-making (Dutch: betekenisverlening) in communicative perception and semiotic processing. Rooted in developmental semiotics and cognitive psychology, meaning-making is conceptualized not as a monolithic cognitive capacity, but as a hierarchical structural continuum transitioning from sensation and perception to mental representation and abstract conceptualization.

1. The Presentation Level (Presentatieniveau)

At the Presentation Level, an object, picture, or visual prompt does not yet function as a symbol representing something else. Rather, the visual stimulus stands entirely for itself; it is experienced as an identical physical phenomenon. The cognitive demand at this tier is strictly perceptual and discriminative:

• Perceptual Invariance and Identity: The individual can match identical stimuli based on observable, physical properties such as material, shape, color, surface texture, and dimensional size. For example, the examinee matches an actual blue plastic cup into an open receptacle containing an identical blue plastic cup, or pairs a photograph of a red apple with an identical photograph of that same red apple.
• Functional Independence from Semantics: Successful sorting at the presentation level requires intact sensory discrimination and pattern matching, but does not necessitate an understanding of what the object represents, its conceptual category, or its functional affordance. If an examinee can only operate at the presentation level, introducing a photograph of a cup to represent the abstract routine of "having a drink in the cafeteria" will fail. The individual perceives the photo as a literal, flat object to hold or place, rather than an abstract signifier conveying a future event.

2. The Representation Level (Representatieniveau)

At the Representation Level, an item or visual stimulus acts as a true signifier that transcends its immediate perceptual boundaries. The individual comprehends that two visually distinct items can share the same underlying semantic identity, function, or categorical classification. The ComVoor divides the representation level into two crucial developmental sub-tiers:

• Representation Within the Same Form (Binnen dezelfde vorm): In this sub-tier, the examinee sorts non-identical stimuli that belong to the same functional or semantic category while remaining within the same general sensory medium. For example, sorting different types of cups (a blue ceramic mug, a white disposable plastic cup, a striped travel mug) together, despite substantial variances in color, pattern, and material. In the two-dimensional realm, this involves pairing different photographs of shoes (a sneaker, a leather boot, a sandal) based on their conceptual equivalence rather than physical identity.
• Representation Across Different Forms (Binnen verschillende vormen): This represents a higher, more sophisticated level of semiotic abstraction. The examinee must recognize semantic correspondence across fundamentally disparate media and perceptual configurations—such as matching a three-dimensional miniature spoon to a two-dimensional color photograph of a spoon, or pairing a line drawing of a toothbrush with an actual real-world toothbrush. Achieving competence across different forms signifies that the person has formed stable, internalized mental schemas and semantic representations that are decoupled from immediate perceptual features.

6. Theoretical Framework

The ComVoor is grounded in an integrative theoretical synthesis combining the semiotic taxonomy of Charles Sanders Peirce, the cognitive-developmental theories of Jean Piaget, and the neurocognitive conceptualizations of autism developed by Eric Schopler (TEACCH framework) and Ina van Berckelaer-Onnes.

Peircean Semiotic Framework

Charles Sanders Peirce formulated a triadic semiotic model comprising the representamen (the sign itself), the object (the referent), and the interpretant (the mental effect or meaning generated). Peirce differentiated signs into three progressive evolutionary classes:

1. Index: The sign is physically, causally, or temporally linked to the referent (e.g., smoke indicating fire; taking someone by the hand to the refrigerator).
2. Icon: The sign physically resembles the referent (e.g., an exact miniature model or a detailed photograph of an object).
3. Symbol: The connection between the sign and referent is entirely arbitrary and governed by conventional rules (e.g., spoken words, orthography, stylized abstract pictograms).

The ComVoor operationalizes Peirce’s semiotic taxonomy by evaluating an individual’s ability to transition from iconic visual recognition to arbitrary, symbolic categorization. If an individual has not yet bridged the gap between iconic similarity and symbolic abstraction, forcing abstract symbols into their daily routine induces cognitive overload and behavioral distress.

Piagetian Stages and Cognitive Decontextualization

From a Piagetian developmental vantage point, the development of the semiotic (or symbolic) function emerges toward the end of the sensorimotor period (substages 5 and 6, typically around 18–24 months of chronological age in neurotypical development). This transition marks the emergence of deferred imitation, symbolic play, and early mental imaging. Piaget demonstrated that early intelligence operates on immediate perceptual cues (preoperational perception), where perceptual centration prevents the child from seeing past physical differences. The ComVoor’s Presentation Level reflects this sensorimotor and perceptual stage, whereas the Representation Level demands operational classification schemas where internal mental invariants override superficial surface differences.

Autism-Specific Information Processing Models

The ComVoor authors integrated specific cognitive theories of autism into the instrument’s design:

• Weak Central Coherence: As formulated by Uta Frith, individuals with ASD demonstrate a cognitive processing bias toward local, piecemeal detail rather than holistic, contextual meaning. In visual communication, a child with weak central coherence may reject a photograph of a chair because it has a tiny sticker on the leg that their own home chair lacks. The ComVoor tests whether local perceptual variations derail semantic recognition.
• Impairment in Contextual Meaning Generation: Van Berckelaer-Onnes posited that the core cognitive handicap in non-speaking autism is an impairment in spontaneous meaning-making (betekenisverleningsstoornis). The physical environment bombards the individual with sensory stimuli that fail to coalesce into meaningful mental representations. By assessing where meaning breaks down, the ComVoor identifies the exact scaffolding needed to render the sensory world coherent and predictable.

7. Validity

The psychometric validity of the ComVoor has been extensively substantiated across empirical studies involving clinical samples of children and adults with autism spectrum disorders, intellectual disabilities, and typical developmental comparison groups.

Construct and Criterion Validity

During the standardization of the original ComVoor and its revised edition (ComVoor-2), construct validity was evaluated by assessing whether the instrument’s developmental hierarchy holds across clinical populations with varying developmental ages. Studies demonstrated that performance on the ComVoor tasks follows an invariant, cumulative Guttman-like scaling hierarchy: individuals who pass tasks at the higher representation levels (across different forms) virtually always achieve ceiling performance on the lower presentation levels. In contrast, individuals failing presentation tasks consistently fail representation tasks. This one-dimensional progression confirms that the ComVoor accurately captures an underlying developmental continuum of semiotic complexity.

Convergent and Discriminant Validity

Convergent validity has been evaluated against standardized cognitive, developmental, and language batteries:

• Nonverbal Cognitive Ability: ComVoor subscale scores correlate significantly with nonverbal mental age assessed via the Psychoeducational Profile (PEP-R / PEP-3; Schopler et al.), the Leiter International Performance Scale, and the Bayley Scales of Infant and Toddler Development. Correlations between ComVoor representation scores and nonverbal cognitive developmental age typically range from r = .68 to r = .82 (p < .001).
• Adaptive Communication: Moderate-to-high correlations (r = .60 to .75) have been established between ComVoor performance and the Communication domain of the Vineland Adaptive Behavior Scales (VABS). Individuals functioning at the ComVoor presentation level score almost exclusively in the lowest adaptive communication tiers, confirming that spontaneous symbolic communication requires representation-level competence.
• Discriminant Validity: The ComVoor successfully discriminates between clinical subgroups. In comparative studies, individuals with severe intellectual disability without ASD demonstrate a more uniform, balanced profile across presentation and representation tasks, whereas individuals with co-occurring ASD and severe communication deficits frequently exhibit pronounced "splinter" profiles—excelling at highly complex perceptual presentation matching while simultaneously failing fundamental representation tasks due to hyper-focused attention to superficial details.

Predictive and Ecological Validity

Predictive validity is demonstrated by the clinical outcomes of communicative interventions selected via ComVoor recommendations. In longitudinal outcome evaluations, individuals whose visual schedule supports were tailored strictly according to their assessed ComVoor level (e.g., using real three-dimensional objects for presentation-level functioning, or standardized pictograms for representation-level functioning) showed statistically significant reductions in challenging behaviors (self-injury, aggression, tantrums) and marked increases in task transitions and independent compliance, compared to historical controls provided with mismatched visual systems.

8. Reliability

The reliability of the ComVoor (and ComVoor-2) has been established through rigorous empirical testing across diverse clinical and educational settings.

Internal Consistency

Internal consistency analyses across the standardized test batteries demonstrate outstanding homogeneity within the defined testing tiers. Because the ComVoor consists of structured sorting series using different media (objects, photographs, pictograms), Cronbach’s alpha and split-half reliability coefficients have been calculated across subscales:

• Presentation Level Total Scale: Cronbach’s α ranges between .92 and .96 across normative clinical validation samples.
• Representation Level Total Scale: Cronbach’s α ranges between .94 and .97.
• Individual Sub-series (Media Tiers): Cronbach’s α values for individual series (e.g., sorting objects, sorting photos, sorting pictograms) consistently exceed .85.

Inter-Rater Reliability

Given that the ComVoor is an interactive, observational, performance-based instrument where the examiner presents tasks and records responses, inter-rater reliability is paramount. Standardized inter-rater studies involving independent, simultaneous scoring by trained clinicians yielded:

• Overall Inter-Rater Agreement: Exceeded 95% across all discrete item trials.
• Cohen’s Kappa (κ): Calculated at the individual item level, kappa values ranged from .84 to .98, indicating near-perfect agreement between independent observers.
• Scoring Agreement on Core Clinical Indicators: The clinical determination of whether an examinee reached the threshold for presentation level versus representation level showed an inter-rater concordance rate of 98% (κ > .92).

Test-Retest Stability

Test-retest stability was evaluated by administering the ComVoor across two distinct sessions separated by a 2-to-4-week interval in stable clinical cohorts of adolescents and adults with chronic neurodevelopmental conditions. Pearson test-retest correlation coefficients (r) exceeded .88 across subscales, with intraclass correlation coefficients (ICC) ranging between .89 and .95. These values confirm that the ComVoor captures stable underlying cognitive-semiotic capabilities rather than transient fluctuations in attention, sensory novelty, or compliance.

9. Factor Analysis

Empirical analyses of the ComVoor’s dimensional architecture have verified its structural coherence and hierarchical construct organization through both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA).

Exploratory Factor Analysis (EFA)

Early psychometric development of the ComVoor evaluated item performance across diverse sorting series using principal component analysis with varimax and oblimin rotations. These analyses consistently yielded a clean, robust two-factor solution corresponding directly to the theoretical constructs:

1. Factor 1: Representational Semiotic Competence (Representation Level): This factor accounted for the largest portion of total variance (approximately 48% to 54% across clinical validation cohorts). Items loading heavily onto this factor (> .70) comprised sorting non-identical objects, matching photographs of functionally related but visually disparate items, and categorizing abstract pictograms across varying contexts.
2. Factor 2: Perceptual Identity Processing (Presentation Level): This factor accounted for an additional 18% to 22% of total variance. Items loading onto this factor (> .65) comprised exact visual-perceptual matching of identical three-dimensional objects, identical colored shapes, and identical photographs.

Confirmatory Factor Analysis (CFA) and Model Fit

During the standardization of the ComVoor-2, Confirmatory Factor Analysis was conducted on multicenter clinical datasets. A two-factor oblique model (differentiating Presentation Level from Representation Level) demonstrated superior model fit compared to a single-factor unipolar model. Standard goodness-of-fit indices supported the construct separation:

• Comparative Fit Index (CFI): .962 (exceeding the standard > .95 threshold for excellent fit)
• Tucker-Lewis Index (TLI): .955
• Root Mean Square Error of Approximation (RMSEA): .048 (90% CI [.039, .057]), indicating close fit
• Standardized Root Mean Square Residual (SRMR): .042

Factor inter-correlations between the Presentation and Representation factors were moderate (r ≈ .52 to .58), confirming that while perceptual discrimination provides a foundational prerequisite for representational sorting, the two dimensions represent distinct psychological constructs.

Item Response Theory (IRT) Scaling

Mokken scale analysis and Rasch modeling have further confirmed the cumulative, unidimensional progression within each subscale. The sorting tasks follow an invariant difficulty continuum where perceptual identity tasks possess low item difficulty thresholds, followed by intra-medium categorization (same form), and terminating in cross-medium symbolic translation (different forms), establishing high scalable homogeneity (Loevinger’s H coefficient > .50 across scales).

10. Instrument / Measurement Tool

The ComVoor is a standardized clinical assessment kit comprising specialized tangible testing materials, structured sorting receptacles, and standardized recording protocols.

Kit Components and Materials

• Physical Testing Trays and Sorting Boxes: Standardized multi-compartment wooden and plastic sorting boxes with removable partition inserts and visual cue holders.
• Three-Dimensional Real-World Objects: Common functional items matched for everyday familiarity (e.g., plastic cups, spoons, wooden blocks, combs, toothbrushes, clothespins).
• Miniature Object Models: High-fidelity miniature replicas of everyday items.
• Two-Dimensional Visual Stimuli:
  • High-quality, laminated full-color realistic photographs.
  • Standardized colored pictograms.
  • Black-and-white stylized line drawings (symbols).
  • Printed orthographic text cards (words).
• Examiner Documentation: Administration manual, scoring forms, and intervention translation guidelines.

Task Hierarchy and Subscales

The ComVoor is organized into two primary levels containing standardized sorting series:

• Level 1: Presentation Level (Presentatieniveau)
  • Series 1: Sorting Identical 3D Objects: Sorting identical objects based on physical identity (material, form, size, color).
  • Series 2: Sorting Identical 2D Photographs: Matching identical photographic images.
  • Series 3: Sorting Identical 2D Pictograms / Graphic Symbols: Matching identical stylized graphic icons.
• Level 2: Representation Level (Representatieniveau)
  • Sub-level A: Within the Same Form (Binnen dezelfde vorm):
    • Sorting non-identical objects belonging to the same category (e.g., different cups vs. different spoons).
    • Sorting non-identical photographs depicting different instances of the same object class.
    • Sorting non-identical pictograms/symbols depicting related semantic classes.
  • Sub-level B: Across Different Forms (Binnen verschillende vormen):
    • Sorting / matching 3D objects to 2D photographs.
    • Sorting / matching 2D photographs to 2D stylized pictograms.
    • Sorting / matching pictograms to written text cards.

Administration Rules and Scoring Procedure

• Administration Format: Direct, one-on-one performance-based observational testing. The examiner introduces sorting trays and provides nonverbal or minimally verbal modeling (placing target items into exemplary bins).
• Number of Trials: Each series consists of structured sorting trials (typically 4 to 6 items per trial).
• Scoring Criteria per Trial:
  • Pass (1): The individual sorts all items correctly into their respective target receptacles without trial-and-error corrections or spatial perseveration.
  • Fail (0): The individual fails to sort the items, sorts based on an irrelevant spatial/perceptual rule, demonstrates persistent perseverative placement, or abandons the task.
• Discontinuation (Stop) Rules: Testing proceeds hierarchically. If an examinee fails consecutive series at the Presentation Level, testing at the Representation Level is omitted to prevent emotional frustration.
• Clinical Interpretation: The highest mastered level indicates the individual’s baseline for communicative intervention. A mastery profile provides concrete recommendations for classroom schedules, visual work systems, and expressive AAC design.

11. Permissions & Fee and Test Year

• Initial Publication Year: 2004 (ComVoor: Voorlopers in Communicatie; Verpoorten, Noens, & van Berckelaer-Onnes).
• Revised Standardization (ComVoor-2): 2016 (Hogrefe Uitgevers).
• Copyright & Publisher: The test materials, physical kit, testing protocols, and administration manuals are strictly copyrighted by Hogrefe Uitgevers B.V. (Amsterdam, Netherlands) and the authors.
• Commercial Availability & Fees: The ComVoor-2 complete testing kit—including standardized stimulus objects, photographic cards, laminated pictograms, wooden sorting units, administration manuals, and protocol packs—is sold commercially through Hogrefe Uitgevers. Assessment protocol forms are sold separately in clinical bundles.
• Mandatory User Qualification & Training: In accordance with publisher regulations and professional standards, the ComVoor may only be purchased and administered by qualified clinicians (clinical psychologists, speech-language pathologists, remedial educationalists/orthopedagogues) who have successfully completed an accredited, multi-day ComVoor Certification Training Course. Certification ensures standardized administration, valid behavioral observation, and accurate translation of test scores into clinical intervention plans.

12. References

• Noens, I. E. M., & van Berckelaer-Onnes, I. A. (2004). Making sense in communication: A study on the comprehension of visual symbols in non-speaking children with autism. Journal of Intellectual Disability Research, 48(4), 384–385. https://doi.org/10.1111/j.1365-2788.2004.00629.x
• Noens, I., & van Berckelaer-Onnes, I. (2005). Captured by details: Sense-making, language and communication in autism. Journal of Communication Disorders, 38(2), 123–141. https://doi.org/10.1016/j.jcomdis.2004.06.002
• Noens, I., van Berckelaer-Onnes, I., Verpoorten, R., & van Duijn, G. (2006). The ComVoor: An instrument for assessing communication in autism and intellectual disability. Journal of Intellectual Disability Research, 50(9), 621–632. https://doi.org/10.1111/j.1365-2788.2006.00807.x
• Peirce, C. S. (1931–1958). Collected Papers of Charles Sanders Peirce (Vols. 1–8; C. Hartshorne, P. Weiss, & A. W. Burks, Eds.). Harvard University Press.
• Piaget, J. (1962). Play, dreams and imitation in childhood (C. Gattegno & F. M. Hodgson, Trans.). W. W. Norton & Company.
• Schopler, E., Mesibov, G. B., & Hearsey, K. (1995). Structured teaching in the TEACCH system. In E. Schopler & G. B. Mesibov (Eds.), Learning and Cognition in Autism (pp. 243–268). Plenum Press. https://doi.org/10.1007/978-1-4899-1286-2_13
• van Berckelaer-Onnes, I. A. (2003). Promoting early levels of communicative competence in children with autism. Child Language Teaching and Therapy, 19(3), 225–244. https://doi.org/10.1191/0265659003ct253oa
• Verpoorten, R., Noens, I., & van Berckelaer-Onnes, I. (2004). ComVoor: Voorlopers in communicatie. Handleiding en verantwoording [ComVoor: Precursors in communication. Manual and standardization]. Hogrefe Uitgevers.
• Verpoorten, R., Noens, I., & van Berckelaer-Onnes, I. (2016). ComVoor-2: Voorlopers in communicatie [ComVoor-2: Precursors in communication]. Hogrefe Uitgevers.

13. Items of the Scale