However one may specifically measure reading performance, any demonstrable behavioral deficiency in reading may be the result of any of several different factors, singly, or in various combinations. The major possible causes are: 1. Technical and attitudinal deficiencies of teachers of reading; 2. emotional block centering on the reading process or somehow associated with it; 3. general intellectual deficiency (whether developmentally slow, arrested, or regressive); 4 organic impairment (whether sensory, motor or integrative, and whether inherited, congenital, or acquired by accident or disease, and whether local or general). This discussion is concerned only with the relations of measured reading deficiency with the 2nd and 4th of these factors. It is recognized, of course, that in actual cases these factors cooperatively determine reading behavior and that there is mutual inter-action among them.By definition for the present paper we shall refer to those instances of reading deficiency whose primary cause is organic as reading disability. The term reading tnability for those cases depending on emotional and intellectual factors.Furthermore, reading disability, an impairment of the mental processes (visual, auditory, vocal) most used in reading, rests upon a structural impairment (Warren 14). These are not the only mental processes involved in reading. Reading more nearly involves the entire mental organization of the individual than is commonly supposed. For example, kinethesis is used in eye movements and in vocalizations. Also, it is likely that the cerebrum operates very much as a unit in "advanced" reading. Furthermore, virtually the entire "apperceptive mass" of sets, memories, stimulus-response associations, etc., participate in reading behavior.This definition results from more than two thousand hours of indi-1 The author was inclined to credit all reading failure to faulty instruction when he began work in this field Actually most children with reading disability had received more, and, probably better instruction in reading than was received by the generality of children from comparable social backgrounds, that is, better in the sense of the technical proficiency of the teaching, not of course, in the wider psychological sense.
