A hindrance to a comprehensive review of literature bearing on anyone of these hypotheses is the large number of unpublished theses and dissertations of relevance, and the fact that. many libraries will not provide inter-library loans of these materials. Since we could not obtain some studies, this review cannot be considered exhaustive.
In this section we will summarize literature bearing on the first of the four hypotheses. The literature reviewed is restricted to studies using somewhat "molar" measures of auding and reading vocabulary and comprehension competencies. By "molar", we mean that the measures used do not permit the detailed analysis found in information-processing studies involving measures such as reaction time differences between auding and reading of words and the like. Rather, the measures included in the reviewed studies are the vocabulary and paragraph comprehension measures typically found in standardized and experimental tests of auding ("listening") and reading.
Some 44 studies were found that appeared relevant to Hypothesis 1, that is, auding performance will exceed reading performance in the early years of schooling and later become equal. Of these 44 studies, 31 were obtained and reviewed with regard to the following: (a) grade level of the students tested; (b) whether or not the same, matched, or independent students were tested under both auding and reading conditions; (c) whether or not the same, equivalent, or just different content materials were used under both auding and reading conditions; (d) whether or not auding and reading conditions were counterbalanced in order of presentation; (e) whether or not reading and auding rate had been equated by matching auding and reading rate; (f) whether or not time for auding and reading had been equated by limiting reading time to the time required to aud the passage; (g) whether or not students were instructed to read the passage through once, taking the amount of time needed, regardless of whether or not this exceeded the auding time; (h) whether the results showed auding performance to be greater than reading performance (A > R), equal to reading performance (A = R), or less than reading performance (A < R). The results of the review are summarized in Tables 2 and 3.