slide loops on itself, the music stops and tries to restart. This continues for as long as the learner continues to hit the switch. The music never gets chance to play and the image (if we time it in) never really appears on the screen. It is only when the learner tires of repeatedly activating the switch that things happen – the image appears and music plays. The computer will not tire before the learner and reinforces the desired behaviour!
The next stage
So s/he can activate a switch and turn on that yapping dog? For how long will that remain motivating? The same old things happening in each session is stagnation and not progression but, sometimes, moving the person forward is both daunting and difficult. For us, the next stage is to introduce another switch – the ‘Null Switch’. The null switch does nothing, it is a bit of a distraction, it is not plugged into anything. The null switch looks different to the active switch. The active switch is labelled, is a different colour and may be a different size. The null switch initially has no label and is not connected to any motivator. Only when the learner activates the active switch is there a reward. Does the learner discriminate? If yes then make the null switch easier to target and the active switch less easy. Does the learner still continue to discriminate the active switch? How far can we take this? The learner who ignores the null switch placed conveniently in front of his/her body and turns and stretches to access the active switch in order to (for example) turn on a TV for 20 seconds is not only demonstrating active discrimination between switches but also cause and effect. This should be recorded as evidence!
When the learner is discriminating (note that we are not claiming that the learner is reading the symbol on the active switch) then we introduce a label to the null switch. The null symbol should be something that is consistently used for this purpose throughout your school or college and only for this purpose. We use a red cross on a white background. Be wary of making claims on success at this point: the learner may not be discriminating between symbols. S/he may be discriminating between some other attribute of the two switches (we should eventually ensure that both switches, the null and the active switch, are identical). S/he may have tried both and then remembered and stuck with the switch that works. S/he may have figured out the ‘game’ … go with the one that is a little more difficult to reach. However, all of these demonstrate learning! We advise caution on the claim that the learner can discriminate between symbols until you are sure that is exactly what is happening.
Multi-Switching versus Scanning
When we have achieved success with symbol discrimination, and we should emphasise that this can take many days, weeks, months (or even years) of work, then we can begin to introduce choices with two or more (four is a practical maximum) switches operating two or more items. Once again, we urge caution about what can be claimed from the success of this venture. Is Adam making a choice if he selects one of two switches that are attached to (for example) a Partner Two and says ‘Orange Juice’ as his preferred choice of drink? No! He could have randomly hit either switch and be rewarded with a favoured drink (Orange or Blackcurrant). However, when he activates the switch with the blackcurrant symbol he gets blackcurrant and when he actives the switch with the Orange Juice symbol he gets orange. How can we be certain that Adam knows one from the other? Ask him! Hold up Orange and say ‘What is this? Adam can use the same switches to name the item. Ah but Adam doesn’t realise that is what you are asking. He thinks that you are offering him a choice of drinks again and that is why he chose the blackcurrant! To be more certain we could introduce a symbol for something that is not a drink and ask again. Even here we can only be reasonably certain that Adam has discriminated the drink symbol from a symbol that is not a drink (We say reasonably because Adam may be selecting on the basis of the most familiar