We frequently experience, when we are doubtful about the spelling of a word, that the greater voluntary exertion we use, that is the more intensely we think about it, the further are we from regaining the lost association between the letters of it, but which readily recurs when we have become careless about it.  In the same manner, after having for an hour laboured to recollect the name of some absent person, it shall seem, particularly after sleep, to come into the mind as it were spontaneously; that is the word we are in search of, was joined to the preceding one by association; this association being dissevered, we endeavour to recover it by volition; this very action of the mind strikes our attention more, than the faint link of association, and we find it impossible by this means to retrieve the lost word.  After sleep, when volition is entirely suspended, the mind becomes capable of perceiving the fainter link of association, and the word is regained.

On this circumstance depends the impediment of speech before mentioned; the first syllable of a word is causable by volition, but the remainder of it is in common conversation introduced by its associations with this first syllable acquired by long habit.  Hence when the mind of the stammerer is vehemently employed on some idea of ambition of shining, or fear of not succeeding, the associations of the motions of the muscles of articulation with each other become dissevered by this greater exertion, and he endeavours in vain by voluntary efforts to rejoin the broken association.  For this purpose he continues to repeat the first syllable, which is causable by volition, and strives in vain, by various distortions of countenance, to produce the next links, which are subject to association.  See Class IV. 3. 1. 1.

11.  After our accomplished musician has acquired great variety of tunes and songs, so that some of them begin to cease to be easily recollected, she finds progressive trains of musical notes more frequently forgotten, than those which are composed of reiterated circles, according with the eleventh preceding article.

12.  To finish our example with the preceding articles we must at length suppose, that our fair performer falls asleep over her harpsichord; and thus by the suspension of volition, and the exclusion of external stimuli, she dissevers the trains and circles of her musical exertions.

III. 1.  Many of these circumstances of catenations of motions receive an easy explanation from the four following consequences to the seventh law of animal causation in Sect.  IV.  These are, first, that those successions or combinations of animal motions, whether they were united by causation, association, or catenation, which have been most frequently repeated, acquire the strongest connection.  Secondly, that of these, those, which have been less frequently mixed with other trains or tribes of motion, have the strongest connection.  Thirdly, that of these, those, which were first formed, have the strongest connection.  Fourthly, that if an animal motion be excited by more than one causation, association, or catenation, at the same time, it will be performed with greater energy.