Learning How to Use Scanning
Scanning is a method of access for speech generating devices and computers. Unlike a direct access method, like eye and head tracking, scanning requires you to activate a switch to control a cursor that moves from one target to the next.
With scanning, when the target message, or item on the screen is highlighted, the client activates a switch, such as Nous - the wearable blink switch, and a message can be spoken out loud or inserted into a line of text.
Switch scanning requires cognitive and motor processes that individuals with severe physical disabilities may find challenging due to the level of attention and concentration need to follow the scan pattern. Compared to other access methods people no neurological impairment perform more slowly and make more errors when using switch scanning access methods. Switch scanning also requires people to time their movements precisely and hit the switch as soon as a desired communication target is highlighted.
Learning to use a switch can be both physically and mentally tiring and challenging for a user. It's important to have time to practice. Research shows that shorter sessions that are spread out through the day are more effective than single sessions of longer duration.
Different types of scanning
There are different types of scanning:
- single switch scanning, where the scanner moves when the client uses their switch, and usually they will use a “dwell” to select, where the option the stop on is selected after a set time.
- Two switch scanning: where the scanner moves when the client uses their switch, and they use a second switch to select the option they wish to select
- Automatic scanner, single switch: where the scanner moves on an automatic time, and the scanner lands on the option the client wishes to select, they use their switch to make the selection.
What does success look like with scanning?
In order to be able to use single switch scanning, clinicians will look for the following abilities:
- track an object as it moves across the screen
- press the switch within a specific time period, while the desired option is highlighted.
In order to progress to use two switch scanning, clinicians will look for the following abilities:
- track an object as it moves across the screen
- understand that each switch has a different function- the first moves the highlight box and the second chooses the highlighted item.
Approaches for teaching single switch scanning
- Pop-up: When something appears on the screen to initiate to the user when to press the switch. For example, when the switch is triggered at the same time as the pop-up appears, the client is rewarded. Another example is to provide your client ~30 seconds to respond, and decrease the amount of time they have to respond as their skill improves. This enables people to experience success without the added time pressure to press the switch.
- Positional: This skill requires clients to track a moving object across the screen and press the switch when it reaches a specific position. This skill mirrors the process of tracking a highlighting scan box as it moves through the choices and pressing the switch when the item of interest has been highlighted.
Approaches for Teaching Two Switch Scanning
Example of two switch scanning
Two switch scanning can offer an increase in activities a user can perform as well as improved independence. When learning this skill, the user needs to understand that each switch has a role to play in completing a given task/activity.
Selecting one or two switches involves moving or tracking an object left to right across the screen through a series of choices. A scan box highlights each choice, and when it reaches the item of interest, the client chooses a switch to select it. Here are some steps that therapists take to teach clients to use two switch scanning:
"Always Right": This stage offers people with numerous activities that enable them to make a variety of choices, without being fearful of getting things wrong. Whatever the choice, it will attract a reward.
By applying the "always right" method, it ensures that the client’s focus is on the process of choosing and avoids over-complications caused by requiring them to answer questions or complete specific tasks. Clients must be encouraged to make choices, and as their confidence increases, therapists can offer some means of structure. For example, making suggestions for selection a specific option to see the outcome.
- Choosing Independently: this stage extends the choosing process beyond "always right", and asks the client to choose specific objects from rows that contain both full and empty cells. The process remains the same, whether using one or two switches for access. If they select a cell that has an item on it they’re rewarded, if they select an empty cell, they’re not.
- Simple Sequences: here, the client is encouraged to complete simple sequences by selecting the appropriate object from three or more options to select from. These involve both empty and filled cells, where the client starts with a row filled with, for example, animals and can choose which ones to add to the farmyard. As animals are chosen, the cells that were selected from become empty, which makes it progressively difficult to select options. Once the client has chosen all the options available, they are rewarded.
- Specific Target: in this stage clients are taught to select a specific object from three or more on screen options in response to a question or request. This stage is the most challenging as it requires clients to locate a specific cell or object and discriminate it from others.