# Developmental Bands for AAC: Evidence-Based Framework (0-36 Months)

Research conducted 2026-05-18 for M1-001 Developmental Level Determination deliverable.

## Foundational Principle: Developmental Bands, Not Age Bands

Age is a poor proxy for communicative ability. Every major clinical AAC framework recognizes this, yet most commercial apps still default to age-based staging.

Five validated frameworks synthesized:
1. Bates, Camaioni & Volterra (1975) — perlocutionary/illocutionary/locutionary stages
2. Rowland & Fried-Oken (2010) Communication Matrix — 7 levels of communicative behavior
3. Dowden (1999) — 3 communicator profiles (emerging, context-dependent, independent)
4. Brady et al. (2012) Communication Complexity Scale — validated for presymbolic/early symbolic
5. Wetherby & Prizant (2002) CSBS — 7 prelinguistic domains

## The Five Developmental Bands

### Band 1: Pre-Intentional Communication (Reflexive/Reactive)
- **Communication Matrix Level:** I (Pre-Intentional Behavior)
- **Bates:** Perlocutionary stage
- **Dowden:** Emerging communicator
- **Typical TD age:** 0-3 months (may persist indefinitely with significant disabilities)

**Capabilities:**
- Communicative: Reflexive behaviors (crying, startling, facial grimacing, comfort sounds) NOT under voluntary control. Caregiver is the meaning-maker.
- Cognitive: Responds to internal states. Beginning state regulation. No cause-effect understanding.
- Motor: Reflexive movements. Head turning toward sound/light. Limited voluntary motor control.
- Sensory: Responds to loud sounds, bright lights, touch. Beginning auditory discrimination.

**Transition markers toward Band 2:**
- Increased alert state duration
- Differential crying
- Quieting to familiar voice
- Visual fixation on people/objects
- Emerging social smile

**Evidence-based intervention:**
- Works: Partner-perceived communication training (Cress & Marvin, 2003), responsive interaction (Yoder & Warren, 1998), environmental enrichment
- Doesn't work: Presenting AAC devices/symbols, waiting for "prerequisites"

### Band 2: Intentional Pre-Symbolic Communication (Emerging Intentionality)
- **Communication Matrix Levels:** II-III
- **Bates:** Late perlocutionary → early illocutionary
- **Dowden:** Emerging communicator
- **Typical TD age:** 3-8 months (intentional), 6-12 months (unconventional pre-symbolic)

**The 9-Month Revolution (Tomasello):**
At ~9-12 months, joint attention emerges. The child begins sharing attention with another person toward an object. Protoimperative pointing ("I want THAT"), gaze alternation, protodeclarative pointing follow. This is THE watershed moment for AAC intervention.

**Capabilities:**
- Communicative: Voluntary behaviors, progressing to intentional. Reaches, vocalizes, gaze alternation, pulls adult's hand toward objects.
- Cognitive: Emerging cause-effect. Contingency awareness. Object permanence beginning.
- Motor: Voluntary reach/grasp. Sitting → independent. Beginning to point.

**Transition markers toward Band 3:**
- Consistent gaze alternation
- Persistent communication attempts when initial fails (repair)
- Conventional gestures (waving, head shaking, pointing)
- Understanding some words even without producing them

**Evidence-based intervention:**
- Works: Prelinguistic Milieu Teaching (Yoder & Warren, 1998, 2002), cause-effect AAC (single-switch), Visual Scene Displays for exposure (Light & Drager)
- Doesn't work: Grid-based displays (Drager et al., 2003), complex navigation, expecting referential symbol use

### Band 3: Conventional Pre-Symbolic / Emerging Symbolic (First Symbols)
- **Communication Matrix Levels:** IV-V
- **Bates:** Illocutionary → early locutionary
- **Dowden:** Emerging → Context-Dependent
- **Typical TD age:** 9-18 months

**The Symbol Threshold:**
The most clinically significant milestone. Shift from pre-symbolic ("I push adult's hand toward cookie") to symbolic ("I point to the PICTURE of a cookie"). Representational understanding — one thing can stand for another. Concrete symbols (photographs, realistic pictures) far easier than abstract symbols at this stage.

**Capabilities:**
- Communicative: Conventional gestures used intentionally. Beginning symbol understanding. May use 1-3 "words."
- Cognitive: Object permanence. Means-end understanding. Emerging pretend play. Categorization beginning.
- Motor: Walking. Pincer grasp. Index finger pointing. Can activate a switch/target.

**Transition markers toward Band 4:**
- Consistent use of a few symbols across contexts
- Vocabulary spurt beginning
- Beginning to combine symbols
- Understanding of 50+ words

**Evidence-based intervention:**
- Works: Aided Language Stimulation (Goossens', Crain & Elder, 1992), VSDs with hotspots (Drager et al., 2003), core vocabulary focus (Banajee et al., 2003 — the 8-12 most functional words), routine-based vocabulary, triple modality (sign + symbol + speech)
- Doesn't work: Large vocabulary sets, abstract symbols before concrete demonstrated, grids >9 cells, treating AAC as secondary to speech

### Band 4: Early Symbolic Communication (Single Symbols → Combinations)
- **Communication Matrix Levels:** V-VI
- **Bates:** Locutionary
- **Dowden:** Context-Dependent
- **Typical TD age:** 12-24 months

**Vocabulary Explosion:**
Banajee, DiCarlo & Stricklin (2003): 96% of toddler utterances use ~23 core words. Overwhelmingly pronouns, verbs, prepositions — NOT nouns. A small set of high-frequency words enables far more communication than a large set of nouns.

**Capabilities:**
- Communicative: Reliable symbol use across contexts. Vocabulary growing toward 50+. Beginning 2-symbol combinations. Expanding pragmatic functions.
- Cognitive: Symbolic play established. Categorization developing. Can remember routines. Can match pictures to objects.
- Motor: Controlled tapping. Can select specific targets. Touchscreen accuracy for large targets.

**Transition markers toward Band 5:**
- Consistent two-symbol combinations
- Vocabulary >50
- Meaningful word order
- Requesting absent objects/events
- Answering simple wh- questions

**Evidence-based intervention:**
- Works: Expanding grid displays (4-9 cells, increase systematically), core + fringe vocabulary model, carrier phrases ("I want ___"), motor planning consistency (LAMP principle), aided language stimulation with 2-symbol combinations
- Doesn't work: Reorganizing layouts (destroys motor memory), massive vocabulary without progressive disclosure, purely taxonomic organization, removing core words to "simplify"

### Band 5: Combinatorial / Early Generative Communication (Sentences Emerge)
- **Communication Matrix Level:** VII (Language)
- **Bates:** Advanced locutionary
- **Dowden:** Context-Dependent → Independent
- **Typical TD age:** 24-36+ months

**Capabilities:**
- Communicative: 2-3+ symbol combinations with word order. Vocabulary 200+. Diverse pragmatic functions. Novel messages (generative language). Pronouns, prepositions, early verb forms.
- Cognitive: Representational thought. Absent objects, past events. Theory of mind emerging. Hierarchical categorization.
- Motor: Precise touchscreen. Page navigation. Grids of 12-20+. Multi-step sequences.

**Evidence-based intervention:**
- Works: Full language system AAC, grammatical scaffolding (morphological markers), expanded grids (6x6+), word prediction, literacy integration
- Doesn't work: Restricting vocabulary, over-reliance on pre-programmed phrases, removing grammatical tools

## Commercial AAC System Staging (None Use Formal Developmental Bands)

### LAMP Words for Life (PRC-Saltillo)
- 3 levels: 1-Hit (84 words), Transition, Full (3000+)
- Motor-planning-based, words stay forever
- "Start at highest level with moderate success" — not developmental
- Weakness: 1-Hit still presents 84 symbols on a grid

### Proloquo2Go (AssistiveWare)
- Crescendo: Basic, Intermediate, Advanced Core
- Grid sizes 2x2 to 11x11 (23 configurations)
- Progressive Language feature for systematic introduction
- Weakness: Even 2x2 is still a grid, no VSD option

### PODD (Gayle Porter)
- 14 templates, pragmatic organization
- Strong on communicative functions
- Weakness: Designed for physical books, limited digital implementation

### TouchChat with WordPower (PRC-Saltillo)
- WordPower 20 through 140 + Gateway templates
- Grid-size-based progression
- Not formally tied to developmental stages

**KEY FINDING: No commercial system uses formal developmental bands tied to communicative milestones. All use vocabulary complexity/grid size. The mapping is left to clinician judgment. This is a differentiator for Meadow.**

## Key Citations

### Assessment Frameworks
- Bates, Camaioni & Volterra (1975) — Acquisition of Performatives Prior to Speech
- Rowland & Fried-Oken (2010) — Communication Matrix clinical/research assessment tool
- Dowden (1999) — Communicator Profiles (emerging, context-dependent, independent)
- Brady et al. (2012) — Communication Complexity Scale validation
- Wetherby & Prizant (2002) — CSBS

### No Prerequisites Evidence
- ASHA Position Statement (2004) — no cognitive, age, or behavioral prerequisites
- Romski & Sevcik (2005) — debunked 6 AAC myths
- Cress & Marvin (2003) — AAC appropriate at pre-intentional stages

### AAC Doesn't Inhibit Speech
- Millar, Light & Schlosser (2006) — meta-analysis, 23 studies, 67 individuals: 89% increased speech, 0% decreased
- Romski, Sevcik et al. (2010) — RCT, early AAC increases vocabulary for ≤3 year olds

### Display Design
- Drager et al. (2003) — 2-3 year olds failed grids, succeeded with VSDs
- Light & Drager (2007, 2010) — VSDs reduce cognitive demands
- Goossens', Crain & Elder (1992) — aided language stimulation gold standard
- Sennott, Light & McNaughton (2016) — aided language modeling review

### Vocabulary & Intervention
- Banajee, DiCarlo & Stricklin (2003) — 96% of toddler utterances = ~23 core words
- Yoder & Warren (1998, 2002) — Prelinguistic Milieu Teaching
- Tomasello (2007) — joint attention at 9-12 months