Clinical Traceability Matrix
The clinical reasoning behind every design choice
This matrix maps Meadow’s design decisions to the Participation Model (Beukelman & Light, 2020) — the standard AAC assessment framework. It answers three questions for each feature:
1. What communication function does this enable?
2. What barrier does it address?
3. What evidence supports the approach?
Use this document as your sign-off checklist. For each row, verify that the design rationale aligns with clinical best practice. The “Deliverable” column links to the full design detail.
Opportunity
- Practice
- Knowledge
- Skill
Access
- Motor
- Cognitive
- Linguistic
- Sensory
Status key
How does Meadow support each major communication function? Each row maps a design feature to the pragmatic function it enables, the barrier it addresses, and where to find the full design.
Requesting
| Design Feature | How It Supports Requesting | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Scene-based vocabulary | Child taps objects in an illustrated kitchen/bathroom/bedroom. Words surface where the child needs them, in context. | Light & Drager (2007): scene displays reduce cognitive demands for beginning communicators | Vocabulary | M1 | |
| Core word edges | “Want,” “more,” “help” are always visible in compass frame edges. Never hidden in menus. | Consistent motor plan reduces selection time 30–40% (Light & Drager, 2007) | Interaction Design | M1 | |
| QuickChat combinations | After tapping “milk,” child sees “want milk” / “more milk” as ready-made phrases. Scaffolds two-word requesting. | Mirrors caregiver expansion (child: “milk” → parent: “want milk?”) | QuickChat | M1 | |
| Sentence engine | Grammar-aware predictions let child build “want cold milk please” — novel multi-word requests with word order scaffolding. | Supports 24–48mo language explosion (Bates & Goodman, 1997) | Sentence Engine | Future |
Refusing & Rejecting
| Design Feature | How It Supports Refusing | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| “No” and “all done” in bottom edge | Always visible, same position every session. Child can refuse at any moment without navigating. Available from Tier 1. | Rejecting is among the earliest pragmatic functions (Wetherby & Prizant, 2002) | Interaction Design | M1 | |
| “Stop” as core verb | Persistent in bottom edge. One tap, immediate speech output. No multi-step interaction required. | Core vocabulary research: stop/no among top 10 most functional words for AAC users | Vocabulary | M1 |
Expressing Feelings
| Design Feature | How It Supports Emotional Expression | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Feelings tray (avatar) | Tap avatar (bottom-left) → 13 emotions with clear face emoji. Tap one → word speaks immediately. No conversation loop. No follow-up questions. | Emotional expression must be low-friction; upset children cannot manage multi-step interactions | Me (Avatar) | M1 | |
| “I love you” — always reachable | Accessible from every screen, every context. Not buried in a category. Permanent and global. | Adam Wing directive (client requirement): “I love you mama” from Taylor testimonial | Me (Avatar) | M1 |
Commenting & Describing
| Design Feature | How It Supports Commenting | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Descriptor edge (top, blue) | “Yummy,” “hot,” “cold,” “big,” “little” — available to modify any noun. Child can comment on qualities, not just request objects. | Descriptor + noun combinations emerge 18–24mo (ASHA milestones) | Interaction Design | M1 | |
| Scene hotspot labeling | Tapping any object in the scene speaks its name. Not just requesting — also labeling (“spoon!” while pointing at a real spoon). | Scene displays support referential labeling (Drager et al., 2003) | Vocabulary | M1 | |
| Sentence engine — adjective + noun | Grammar-aware suggestions allow “big banana” or “yummy pancakes” — descriptive comments, not just requests. | Modifier + noun is a key word-combination milestone | Sentence Engine | Future |
Social Routines & Greeting
| Design Feature | How It Supports Social Functions | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Social words in bottom edge (purple) | “Please,” “thank you,” “hi,” “bye” always visible. Supports social pragmatics without navigating away from current activity. | Social routines are among first pragmatic functions mastered (Bruner, 1983) | Interaction Design | M1 | |
| People edge (right, yellow) | “Mama,” “dada,” “baby,” “me” — named people always accessible. Enables directed social speech (“hi mama,” “bye dada”). | Person + action combinations emerge early (Bates, 1976) | Interaction Design | M1 |
Directing Others
| Design Feature | How It Supports Directing | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Person + verb combinations | Child taps “mama” from right edge, “help” from bottom edge. Two-word directive at Tier 2. | Agent + action is a key semantic relation at MLU 1.5–2.0 | QuickChat | M1 | |
| Sentence engine — person + verb + object | Grammar-aware predictions scaffold “mama help open juice” — agent + action + object + object. | Three-element combinations (MLU 2.5+) emerge 24–36mo | Sentence Engine | Future |
Answering & Responding
| Design Feature | How It Supports Answering | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| “Yes” and “no” in bottom edge | Always visible, always available. Parent asks “Do you want milk?” — child taps “yes.” No navigation required. | Yes/no comprehension typically established by 12–15mo | Interaction Design | M1 | |
| Scene vocabulary as choice board | Parent holds up two items: “Banana or toast?” Child taps their choice in the scene. The scene functions as a visual choice board. | Choice-making is a foundational pragmatic skill (Reichle & Sigafoos, 1991) | Vocabulary | M1 |
How Meadow addresses each access barrier
The Participation Model identifies four access barrier categories. Here’s how Meadow’s design systematically addresses each one, cutting across all communication functions.
Children in the target population may have limited fine motor control, imprecise reach, or emerging intentional movement.
- 60pt minimum touch targets across all tiers
- Motor plan stability — words never move between sessions or tiers
- Switch Control support — full scan-group navigation
- Single-tap speech — no drag, no long-press, no multi-step sequences to speak
- Engagement timer fallback — companion cycle advances if no tap detected
Interaction Design §10 · Companion §10
M1Pre-symbolic and emerging symbolic communicators cannot yet use abstract symbol systems. Cognitive load must be minimized.
- Scene displays for Tier 1 — no symbolic abstraction required
- Tiered complexity — 17 words at Tier 1, 36 at Tier 2, 49+ at Tier 3
- Contextual vocabulary — words appear where they’re needed (kitchen shows food)
- No hierarchical menus — flat navigation, one tap to any scene
- Visual + auditory + gestural redundancy — three channels carry the same meaning
Developmental Foundations · Compass Frame Tiers
M1Children are at different stages of language development. The system must support single words through multi-word utterances without requiring linguistic competence the child hasn’t yet developed.
- Tier-appropriate complexity — single words (T1), two-word combos (T2), sentences (T3)
- Core word vocabulary — aligned with SLP-standard core word boards
- QuickChat scaffolding — offers combinations the child can select, not construct
- Grammar-aware sentence engine — handles word order so the child doesn’t have to
- Fitzgerald Key color coding — visual grammar cues (nouns = orange, verbs = green, etc.)
The target population is primarily language-delayed, not visually impaired — but robust multi-sensory design benefits all learners and supports co-occurring conditions.
- Triple modality — every word is seen (picture), heard (speech), and signed (ASL)
- VoiceOver support — every interactive element has an accessibility label
- High contrast — Fitzgerald Key colors tested for contrast ratios
- Parentese prosody — exaggerated vowels, slower tempo in companion voice
- Dynamic Type — labels scale for low-vision co-users (parents, grandparents)
Companion §04 · Interaction Design §10
M1Beyond the device — supporting the people around the child
Access barriers are about the device. Opportunity barriers are about the people, practices, and systems around the child. Meadow addresses these through design decisions that shape how the SLP, parent, and child interact with the app.
The SLP and parent need consistent, structured ways to use the device in therapy and at home.
- Companion engagement mode — structured, repeatable learning cycle (spotlight → present → wait → celebrate → advance) that SLPs and parents can activate identically
- Routine-based scene organization — scenes match daily activities (mealtime, bath, bedtime), so the app maps to existing therapy and home routines
- Time-aware routine glow — scene tiles suggest the right context at the right time of day
- Parent gate — prevents accidental configuration changes during therapy
Parents may not know how to support AAC use at home. The app must model best practices through its own behavior.
- Companion models language — parentese prosody, expectant pausing, and expansion are demonstrated by the companion so the parent sees what good modeling looks like
- Sub-60-second onboarding — minimal setup burden means the parent doesn’t need to be trained before the child can start using the device
- SLP-led configuration — tier, scenes, and voice are set by the SLP at deployment; parent doesn’t need to make clinical decisions
The child needs to learn that the device is a communication tool — and that they have agency over it.
- Cause-and-effect at Tier 1 — any tap produces a word. Builds the foundational insight that the device responds to the child’s actions
- Guided discovery via companion — spotlight + present + wait cycle teaches word meanings through structured repetition
- Triple modality — redundant channels mean the child can learn through whichever modality they attend to
Developmental Foundations · Companion
M1Meadow must function as an E2510 speech generating device under funded-device regulations.
- Communication-first identity — speech output is the primary function; teaching features are supplementary, not primary
- No data collection — no analytics, telemetry, or off-device data flow in core communication path
- Offline-first — no network dependency for any communication function
- No third-party SDKs in communication path
Sentence Engine
| Capability | Clinical Rationale | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Grammar-aware predictions | After “want,” engine suggests nouns. After “big,” suggests nouns. Scaffolds word order without requiring the child to know grammar rules. | Supports transition from formulaic to generative language (Bates & Goodman, 1997) | Sentence Engine | Future | |
| Morphological modification | Add -ing, -s, -ed to verbs. “Eat” becomes “eating.” Expands grammatical complexity without new vocabulary. | Brown’s Stages: morphological endings emerge Stage II–III (MLU 2.0–3.0) | Sentence Engine | Future |
Word Explorer
| Capability | Clinical Rationale | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Multiple visual representations | Tap “cup” and see 4 different cups (red, blue, sippy, travel). Builds generalization — “cup” isn’t just the one in the picture. | Generalization is a core AAC training goal; single-image symbols can create overly narrow referents | — | Future |
Gamified Sentence Builder
| Capability | Clinical Rationale | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Sentence construction as play | Drag word tiles into sentence slots. Visual feedback for correct word order. Bridges communication tool and learning game for older children (4–5+). | Structured play supports metalinguistic awareness in late preschool | — | Future |
Speak With Me
| Capability | Clinical Rationale | Barrier Addressed | Evidence | Deliverable | Status |
|---|---|---|---|---|---|
| Extended engagement cycles | Longer, more structured learning sessions with the companion. SLP-configurable word targets. Progress tracking across sessions. | Milieu Teaching with structured targets increases intentional communication (Yoder & Warren, 2002) | — | Future |
At a glance
How to use this for sign-off
For each communication function in Section 02, verify that the design features adequately support the child’s ability to perform that function at each tier. For each barrier category in Sections 03–04, verify that the accommodations match the needs of the target population. Follow the deliverable links for full design detail.
Items marked Future are included for directional feedback. They do not require sign-off at this stage but benefit from early clinical input on whether the approach is sound.