92 PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



approximately equally good instruments there maybe a further criterion 

 of expediency. Experimental psychologists have spent, in the aggre- 

 gate, an unduly large amount of time in developing various types of 

 exposure apparatus to satisfy various experimental demands. The 

 excuse for using a new form in these experiments was a new combination 

 of experimental demands and expediency. 



The most generally recognized criteria of a satisfactory exposure appa- 

 ratus 1 relate to the type called the tachistoscope. But the demand 

 for tachistoscopic exposure, that is, for the most rapid possible exposure, 

 is certainly not universal. It has probably been overvalued where it is 

 most useful, that is, in the effort to isolate a single act of vision. It 

 is entirely possible to produce experimental circumstances in which 

 extreme shortness of exposure and consequent uncontrolled adequacy 

 of exposure may be quite undesirable. This is doubtless the case in 

 memory experiments. We believe that it is also the case in all associa- 

 tion experiments, where the first condition of a satisfactory association 

 process would seem to be the least practicable interference with the 

 normal and adequate perception of the stimulus word. 



If it is true in reading, as the evidence seems to point, that the normal 

 visual perception of a word is a complex of stimulation and inhibition 

 processes which may be more or less separated in time (Dodge, 2 pp. 

 55-60), it would seem that the most satisfactory condition for the read- 

 ing reaction would be to combine all the processes in the same instant, 

 as far as practicable, and to increase to a maximum the visual controls 

 that ordinarily complete the process which is begun in the prefixational 

 perception of a word. In other words, the stimulus word of adequate 

 size should appear suddenly, after a signal, all at once, in the field of 

 clear vision, with provision for satisfactory adaptations to distance and 

 illumination. After adequate exposure the persistence of the stimulus 

 word has relatively little or no significance. It may serve a useful 

 function as a control for misperception. 



Our experimental requirements distinctly excluded the tachistoscope 

 type of apparatus. Our positive instrumental demands may be sum- 

 marized as follows: (1) In order to exclude disturbing pre-judgments 

 from partial visual exposure, and to give a definite amount of total 

 exposure, the exposure should be rigidly simultaneous and as nearly 

 instantaneous as possible (cf. Erdmann and Dodge 3 ). (2) To facil- 

 itate the calculation of latency, the moment of total exposure should be 

 related in some constant way to a registrable process. (3) The obvi- 

 ous visual requirements of adaptation to illumination and to the place 

 of exposure in all dimensions must not be transgressed. (4) Since the 



'Whipple, Mental and Physical Tests, Baltimore, 1910, p. 223. 



2 Dodge, An Experimental Study of Visual Fixation. Monograph Supp. of thePsychol. Review, 

 No. 35, 1907. 

 3 Erdmann and Dodge, Psychologische Untersuchungen iiber das Lesen, Halle, 1898, p. 94 



