Page:Mind (New Series) Volume 15.djvu/348

334 w. MCDOUGALL : prepared to admit a similar power of re-enforcing ideas of other kinds. The essential determinant of the direction of sensory atten- tion, apart from the intensity, novelty or other compelling features of the sensory stimuli, is the cerebro-ideational activity, the play of excitement among the organised systems of neural elements of which the higher levels of the brain are composed. We have to suppose that these systems are in part congenitally determined, have a congenital tendency to assume in the course of development certain forms and connexions, but that throughout the course of growth and education they become perpetually modified, extended and inter-connected in the way sketched in masterly fashion by Prof. Stout in his Analytic Psychology. OEG-ANISED NEUEAL DISPOSITIONS AS FACTORS OF THE ATTENTION-PROCESS. Assuming the existence of organised neural dispositions, corresponding on the neural side to the mental dispositions or mental or apperceptive systems described by Prof. Stout, I report in this section certain observations which seem to throw light upon their relations to one another and to the sensory processes and upon some of their functional peculi- arities. At the end of the first paper of this series (p. 349, vol. xi.) the following problems were defined as remaining for solu- tion : (1) What conditions determine the penetration of the excitation-process initiated in a sense-organ to paths of the higher levels of the brain ? (2) to any one such path in preference to other possible paths of the higher levels ? (3) What conditions determine the perpetual shifting of the excitation-process or current of nervous energy from one higher-level path to another? (4) What conditions confine it at each moment to any one such path ? The first and second of these questions have been partially answered. We have seen that besides the conditions of the stimulation of the sense-organs important factors are : (1) The general con- ditions of the brain as regards the quantity of free nervous energy or neurin in it, this depending largely upon the inflow of energy by all the afferent nerves, especially the afferent nerves of the viscera through which, or some of which, the organic sensations are excited ; (2) the adjust- ments of the sense-organs which not only directly favour the reception of some one part of the total mass of sense-stimuli but indirectly, through the afferent impulses initiated by