The functions observed in Nigel's Phase I did turn out to be those of the initial hypothesis. This ceases to be true in Phase but in onc important respect the hypothesis fails already-there is no sign of a developmental progression within the first four functions. As a matter of fact the only two expressions recorded before nine months that fulfill the criteria for language were in the interactional and personal areas. Furthermore, the imagina- tive function seems to appear before the heuristic, although reinterpretation of certain elements(the'problem area' which is referred to in the next paragraph) in the light of Phase II observa tions suggests that this may be wrong, and that the heuristic function begins to appear at NL 4(19HI5 months, at the same time as the imaginative. The two are closely related: the heuristic function is language in the exploration of the objective environ ment-of the"non-self" that has been separated off from the self through the development of the personal function while the imaginative is language used to create an environment of one own, which may be one of sound or of meaning and which leads eventually into story, song and poetry. Finally, the informative function has not appeared at all. What does emerge as some sort of developmental sequence, in Nigel's case, is(i) that the first four functions listed clearly precede the rest, and(ii) that all others precede the informative. The informative function does not appear until nearly the end of Phase II, round about NL 9(21 221 months) but this was not entirely unexpected, since the use of language to convey information is clearly a derivative function, one which presupposes various special conditions including, for one thing, the concept of dialogue. The functions themselves, however, emerge with remarkable clarity. Not only did it prove surprisingly easy to apply the general criteria for identifying a vocal act as language(since the learning of a system cannot be regarded as a function of that system anything interpreted as linguistic practising was left out-as already remarked, Nigel did very little of this); it was possible, throughout NL 1-5, to assign utterances to expressions expressions to meanings and meanings to functions with relatively little doubt or ambiguity. There was one significant exception to this, a problem area lying at the border of the interactional and the personal functions, which proved extremely difficult to system atize; subsequent interpretation suggests that it was, in fact, the