1Eyes + head? In the text we have mentioned that you should try to distinguish between occurrence of movements which are either:- eyes only; head only; or both eyes and head.

It is not necessary to be able to do both head and eye movements. However, you should be sure to give enough time for the learner to 'organise' a response. Often one movement can precede the other. If the stimulus is sufficiently close, the learner may be able to follow it with eyes only.