Investigation of user interface design guidelines to make the computer accessible to mentally retarded adults

An exploratory study was conducted to determine if adults diagnosed as having moderate developmental disability could successfully use a personal computer and, if so, the input devices preferred and the user interface design factors to be considered when designing or selecting interactive applications for this population. Participants in the three-phase study were men and women aged 25-60 living in group homes sponsored by a social services agency. All had been professionally evaluated as moderately mentally retarded.

Phase I observed reaction of participants, none of whom had ever used a computer, to two input devices (mouse and touchscreen) and a graphical user interface. Phase II built on Phase I observations to design a within-subject usability test to gather heuristic data on input devices and to develop user interface guidelines for the target population. In Phase III, a prototype was built to test the effectiveness of these guidelines. Phase I found participants successfully used a graphical user interface and most could use the mouse. In Phase II, which tested mouse, trackball, and touchscreen, the mouse was preferred, although its drag-drop times were longer. Reasons given were less fatigue and greater control of icons.

The Phase III prototype consisted of two games: "Shopping," to teach money handling skills, and "Getting Dressed," to teach a basic life skill. Testing found the participants preferred screens that allowed them to control the action, that quick or unexpected screen responses were upsetting, and that strong visual feedback was important. For example, "Shopping" was redesigned to enable users to visualize purchases by dragging pictures into a shopping cart.

This exploratory study found that developmentally disabled persons could use commercial computer hardware and applications effectively and were proud of their newly developed computer skills. It also derived user interface guidelines for the selection or design of applications for use with this target group. Recommendations are made for a follow-up field study to investigate the applicability of the derived guidelines to a larger population of developmentally disabled persons.