Adapting a grid into a microswitch to suit simple hand movements of a child with profound multiple disabilities

We adapted a grid into a microswitch for the hand movements of a girl with profound multiple disabilities who lay on her back. The grid, suspended above the girl's face, was equipped with two mercury devices, i.e., small sealed ampoules containing a mercury drop and ending with conductive leads. A lateral or forward movement of the grid would make the mercury drop of at least one device slide to the conductive leads and activate the device. During the intervention, activations of the devices, i.e., microswitch activations, produced the occurrence of favorite stimuli. Analysis showed that the girl increased the frequency of hand movements and microswitch activations during the intervention phases compared to the baseline phases (when the favorite stimuli were not available). The increase was retained at a 1-mo. postintervention check.