Scratch Card
Scratch Card is a motor engagement and relaxation activity where the participant scratches away a grey cover layer to reveal a hidden illustrated scene. While not a standardized neuropsychological test, it functions as a low-demand filler, warm-up, or engagement activity. The recorded scratch path and coverage data map onto fine motor control, motor persistence, processing speed, and engagement behavior.
ActivitySpec: lamp.scratch_card
Cognitive domain: Motor engagement, fine motor control, relaxation
Configuration
| Setting | Description |
|---|---|
| Threshold | Percentage of the card that must be scratched before the completion prompt appears (default: 80%). The participant can continue scratching past this point. |
| Number of Cards | Number of scratch cards to present, 1-5 (default: 3). Each card shows a unique scene with no repeats within a session. |
API settings fields
| Dashboard Setting | API Field | Type | Default |
|---|---|---|---|
| Threshold | threshold | number | 80 |
| Number of Cards | num_cards | number | 3 |
| Path Sampling Interval | scratch_path_interval_ms | number | 50 |
Sample Instructions
"Scratch the surface with your finger to reveal the hidden image. Keep scratching until the full picture appears."
Usage
The participant scratches a grey cover layer by dragging their finger (or mouse) to reveal one of five illustrated SVG scenes (tree reader, lake boat, stargazer, garden, sleepy cat). A progress bar shows the percentage scratched, and a card counter tracks progress through the session.
When coverage reaches the configured threshold, a "Next Card" (or "Finish" on the last card) button appears — but the card does not end automatically. The participant can continue scratching past the threshold, and the gap between the threshold and final coverage percentage serves as a behavioral measure of completionism.
Scratch path coordinates and element bounding boxes share the same normalized (0-1) coordinate system, enabling direct spatial overlap analysis.
Scoring
Each card is scored by whether the threshold was reached and the final coverage percentage. The overall score is the proportion of cards completed.
Data
static_data
| Field | Type | Description |
|---|---|---|
num_cards | number | Number of cards configured |
cards_completed | number | Cards where threshold was reached |
cards_attempted | number | Cards the user started scratching |
total_scratch_time_ms | number | Sum of scratch time across all attempted cards (ms) |
avg_scratch_time_ms | number | Average scratch time per attempted card (ms) |
threshold | number | Configured threshold percentage (0-100) |
card_results | array | Per-card detail (see below) |
score | number | Completion percentage |
correct_answers | number | Cards completed |
total_questions | number | Total cards |
questionnaire | object | Post-game ratings: clarity (1-5), happiness (1-5) |
Each entry in card_results:
| Field | Type | Description |
|---|---|---|
card | number | Card number (1-indexed) |
background_name | string | Scene identifier (e.g., "tree_reader", "lake_boat") |
time_ms | number | Time spent scratching this card (ms) |
final_pct | number | Actual percentage scratched (0-100, may exceed threshold) |
threshold_reached | boolean | Whether coverage met the threshold |
elements | array | Visual element bounding boxes for spatial analysis: {name, x, y, w, h} (all normalized 0-1) |
scratch_path | array | Sampled pointer trajectory: {x, y, t} (x/y normalized 0-1, t = ms since card start) |
temporal_slices
One entry per card attempted:
| Field | Type | Description |
|---|---|---|
item | number | Card number (1-indexed) |
type | boolean | true if threshold was reached |
value | number | Final scratch coverage percentage (0-100) |
duration | number | Time spent on this card (ms) |
level | number | Always 1 |
background_name | string | Scene identifier |
Cortex Features
No Cortex features are currently available for this activity.
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