Why is switch scanning so difficult for most of our pupils?
What, if anything, can we do to practically improve it ?
I have known only one pupil who has successfully used switch scanning to access a speech machine and an electric wheelchair; he was an exceptional individual.
The purpose of switch scanning is to exercise choice from a number of items using a two state input device.
A scanning grid is one method of presenting a number of choice items for someone who has a restricted input through a simple on/off switching device. Generally the choice items are displayed in a line or grid and a highlight indicates which item from the grid is active (can be choosen). The highlight can either be visual or audible, ie. the items change colour in turn or give a specific audible message (which could be speech). In one switch scanning the highlight moves through the items automatically (autoscan). In two switch scanning one switch is usually used to move the highlighter and the other to selected the choosen highlighed item.
There are three, four eight switch scanning methods possible with group, user, toggle, same switch, swap switch, and restarting scans possible. They are not usually implemented on common computer programs, and most of them merely allow fine tuning of the scanning method.
What is the fundamental problem with switch scanning ?
The reason for using scanning is to allow an individual with restricted movement to choose from a multiple array.
The individual is extreemly complex, capable of choosing many items.
The connection between them is a simple on/off switch.
The computer is less complex but still capable of choosing many items.
The difficulty thus appears obvious.
The individuals complex choices have to be simplified and constricted to a simple switch on/off. The simple switch on/off has to be expanded by the computer to make a complex choice.
To improve scanning access
1. Improve the switch.
With an on/off switch there isn't much to improve, it either works or it doesn't.
you can improve the pupils ability and speed at using the switch but this option is limited with our students.
2. Improve the computer.
They are improving in speed and processing power. They will soon be able to cope with all the scanning methods mentioned above, perhaps even learning about and accommadating the switch actions of the individual by showing some artificial intelligence.
3. Expand the the connection between the individual and the computer.
This is I feel an area that could be investigated. there could be less constriction in the flow of information between the two participants.
Variable switching
In order to increase the amount of information passed to the computer by the switching mechanism some degree of variable switching could be possible.
The most obvious variables are time, and pressure.
If a scanning highlight moved along the line of items in response to the degree of pressure exerted then a precise choice could be made at once.
If the scanning highlight moved along the line of items in response to the time the switch was activated the precise choice could be directly made.
I realise these are very difficult concepts and control for SLD students but in this scheme there is some learning capable of being developed in switch operation. The student can improve his or her own operation and is not wholly reliant on the computer. In a normal scan a student might be more accurrate in a particular part of the grid, yet the layout is fixed and unchangeable, the same switch movement is used for all switch activations and no improvement in physical access is possible other than the operator (teacher/therapist) increasing the speed of scan. It is a closed system.
In varaiable switching the pupil can leran to operate the switch physically better, improvement is possible in a more open system.
The internal operation of the switch could be controlled to make the switch behave as a normal press on/off switch, acting as a normal pressure pad or press switch.
Piezzo electric discs seem ideal for this purpose.