The explanation of those early omissions and alterations is probably a rather complex matter. To begin with, the speech-organs of a child may lose special aptitudes by the development of other and opposed aptitudes. A friend of mine, a physiologist, tells me that his little boy who said ‘ma-ma’ (but not ‘da-da’) at ten months lost at the age of nineteen months the use of _m_, for which he regularly substituted _b_. He suggests that the nasal sound _m_, though easy for a child in the sucking stage and accustomed to close the lips, may become difficult later on through the acquisition of open sounds. It is worth considering whether this principle does not apply to other inabilities. This, however, is a question for the science of phonetics. We must remember, further, that it is one thing to carry out an articulatory movement as a child of nine months carries it out, ‘impulsively,’ through some congenitally arranged mode of exciting the proper motor centre, another thing to carry it out volitionally, _i.e._, in order to produce a desired result. This last means that the sound-effect of the movement has been learned, that the image or representation of it has been brought into definite connexion with a particular impulse, _viz._, that of carrying out the required movement: and this is now known to depend on the formation of some definite neural connexion between the auditory and the motor regions of the speech-centre. This process is clearly more complex than the first instinctive utterance, and may be furthered or hindered by various conditions. Thus a child’s own spontaneous babblings may not have sufficed to impress a particular sound on the memory; in which case his acquisition of it will be favoured or otherwise by the frequency with which it is produced by others in his hearing. It is probable that differences in the range and accuracy of production of sounds by nurse and mother tell from the first. The differences observable in the order of acquisition of sounds among children may be in part due to this, and not merely to differences in the speech-organ. It is probable, too, that children’s attention may be especially called to certain sounds or sound-groups, either because of a preferential liking for the sounds themselves, or because of a special need of them as useful names. M.’s mother assures me that the child seemed to dislike particular sounds as _j_, which she could and did occasionally pronounce, though she was given to altering them.[86] Another lady writes that her boy at the age of twenty-two months surprised her by suddenly bringing out the combination ‘scissors’. He had just begun to use scissors in cutting up paper, and so had acquired a practical interest in this sound-mass. ----- Footnote 86: The same child, capriciously as it might look, would sometimes avoid _y_, as in saying ‘esh’ for ‘yes,’ though she regularly used this sound as a substitute for _l_, saying ‘yook’ for ‘look,’ and so on. -----