CATPro: context-aware task prompting system with multiple modalities for individuals with cognitive impairments
Wan Chih Chang · 2008 · Proceedings of the 10th International ACM SIGACCESS Conference on Computers and Accessibility (Assets '08) · doi:10.1145/1414471.1414549
Summary
This short paper presents CATPro (Context-Aware Task Prompting), a system designed to help individuals with cognitive impairments perform daily living and workplace tasks more independently. The system targets people with a range of conditions including traumatic brain injury, cerebral palsy, intellectual disability, schizophrenia, dementia, and Alzheimer's disease, developed in collaboration with NGOs running supported employment programs for people transitioning from institutional to community care. CATPro consists of three components: Bluetooth beacon modules deployed in the workplace, a handheld PDA carried by the user, and a status monitoring system for carers. Bluetooth beacons are placed at task locations (e.g., near trash cans, glass windows for janitorial tasks) with a deliberately reduced transmitting radius of 1.5 to 2.0 meters. When a user approaches a designated location, the PDA automatically triggers context-appropriate task prompts — displaying situational photos and delivering voice-over instructions such as "Next, put the glass to the upper-right side of the plate" or "Remove the trash and vacuum the room." The system design draws on psychological models of cognitive processing, usability studies of interfaces for people with cognitive impairments, and requirements gathered from interviews with nurses and job coaches at rehabilitation hospitals.
Key findings
A field test was conducted in a university building covering approximately 10m by 30m across a 5th floor, with Bluetooth modules deployed at three rooms. Five temporarily able-bodied subjects (undergraduate and graduate students) each completed 12 trials with 3 tasks per trial. The system generated 180 total prompts with a 100% success rate — all beacon-enabled prompts triggered precisely at designated locations and users received correct voice-over instructions with situational images. Prompt generation time was 1.5 to 2.1 seconds from beacon pickup to prompt rendering. The system provides multiple modalities to accommodate different situations: during "hands busy" periods, users rely on vibrations and voice reminders rather than visual prompts; photos are used for effective self-reminding with less cognitive load. An important design consideration is that the system avoids negative associations with assistive devices by not constantly reminding users of tasks — instead, prompts appear only when approaching new task locations or when items are missed. Task completions and misses are tracked via optional RFID tags on target objects, with wrist scanners reporting back to the PDA. A dual interface allows carers to monitor status remotely through a console.
Relevance
CATPro addresses a critical gap in workplace accessibility for people with cognitive impairments — the need for just-in-time, location-aware task support that does not require a human "shadow" team. The context-aware approach (prompts triggered by physical proximity rather than timers or manual activation) reduces cognitive load by delivering information exactly when and where it is needed, which is a key principle in designing for cognitive accessibility. The multimodal design — combining visual photos, voice-over, and vibration — demonstrates thoughtful consideration of varying cognitive and situational needs. For accessibility practitioners, the system illustrates several important design principles: avoiding stigma by not over-prompting, supporting employment independence rather than just daily living, and involving rehabilitation professionals in the design process. While the field test used non-disabled participants (due to ethical and safety requirements for testing with the target population), the 100% prompt accuracy provides confidence in the technical foundation. The work highlights the potential of ubiquitous computing technologies like Bluetooth beacons and RFID for creating accessible, context-responsive environments.
Tags: cognitive disability · task prompting · context awareness · supported employment · ubiquitous computing · Bluetooth beacons · assistive technology · independent living · multimodal interaction