We would like to express our thanks to the children, their parents and staff and the special school where this project had its base. Without their valuable contributions and feedback this research would not have been possible. We would also like to thank DynaVox Systems Ltd for supplying the communication devices to run our system on. This research was supported by the UK Engineering and Physical Sciences Research Council under grants EP/F067151/1, EP/F066880/1, EP/E011764/1, EP/H022376/1, and EP/H022570/1Publisher PD
