3Further Reading on Eye Coding: Nolan C (1987; play,1989) Under the Eye of the Clock. Pan.

4Further Reading on Generalisation: Bower TGR & Wishart JG (1972) Stages in the development of the object concept. Cognition 1(1).

5See Appendix II for information on obtaining software for use in enhancing contrast.

Colour perception

: If the learner can track objects (Section 12) and you would like to improve your knowledge about his perception of colour, you might want to try this technique. Present a ball of one colour and roll it back and forth. If he follows the movement consistently, then roll it from side to side through a tunnel (or behind a screen) to emerge at the other side. If he follows the ball and then becomes disinterested, have a different coloured ball emerge. If surprise is registered, you then know he can perceive the difference between these two colours.