Augmentative and Alternative Communication - Access and Selection Methods

Access and Selection Methods

Technological advances have dramatically increased the types of selection methods available for individuals with communication impairments. In "Direct Selection", the selection is made by pointing to the desired symbol using a finger or an alternative pointer, such as eye gaze, a head stick, head- or eye-controlled mouse. To accommodate motor control difficulties some users use alternative activation strategies; for example in "timed activation", the user maintains selection of the symbol for a predetermined period of time until it is recognized by the system. With the "release activation", the selection of the item is only made when the person releases contact from the display.

Direct activation of an AAC system is generally the first choice of access method as it is faster and cognitively easier. Those unable to do so may use indirect selection or "scanning". In this method, items displayed for selection are scanned; the scanning may be visual using indicators such as lights, highlighting, and/or contrasting borders, or auditory using spoken prompts from a communication partner or device. When the desired message is reached, the AAC user indicates the choice using an alternative selection technique such as a switch, vocalization or gesture. Several different patterns for switch access scanning are available: in "circular scanning", the items are displayed in a circle and then scanned one at a time. It is often introduced first to children or beginning AAC users because it is the easiest to understand. In "linear scanning", items are organized in rows and are scanned one at a time until a choice is made. Although more demanding than circular scanning, it is still easy to learn. Finally, in "group-item scanning", items are grouped and the groups scanned consecutively. Once a particular group is selected, items within the group are scanned. One of the most common group-item strategies is row-column scanning in which each row forms a group. The rows of items are scanned and when a row is selected, the items in the row are scanned one at a time until a message is selected.

There are three main selection control techniques in scanning. In "automatic scanning", the scan proceeds at a pre-determined speed and pattern until the user selects an item. In "inverse scanning", the switch is held down to advance the scan, and released to choose the desired iem. In "step scanning", the AAC user activates one switch to move the indicator through the items, and another switch to select the item.