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The Status of Audio-Visual Instruction 15
The graph on pages 16 and 17 presents a picture of audio-visual developments during the past fifty years. It should be kept in mind that the approximate dates indicated refer to the introduction of these various teaching aids among schools. In most instances these now valuable scientific aids to learning were used several years in industry or for entertainment before they were applied to classroom teaching. This has been true of the glass slide (magic lantern), stereograph, phonograph record, motion picture, filmslide, disc recorder, and sound amplifying and distributing equipment. Sound filmslides and recordings of radio programs (transcriptions) are just beginning their effective use among schools, although they have been used several years in industry. On the other hand, the very recent developments in television and facsimile are now being used experimentally among schools. Thus the lag between scientific developments and their use for teaching purposes is decreasing and indicates greater alertness among those who guide the education of youth.
The varying widths of bars of the accompanying graph are intended to indicate (1) the approximate extent to which these teaching aids were or are being used among schools, and (2) the approximate variation in their use from year to year. No attempt has been made to indicate minor variations due to the first World War or during the periods of economic adjustment which followed. Those would have been difficult to estimate with any great degree of accuracy and would add little to the over-all picture.
It is significant that so many of the most effective teaching aids now used extensively among schools have been introduced so recently. It is of still greater significance that, of all the different types now in use, only one has decreased in importance as a teaching aid — the 35 mm. silent motion picture. This is entirely logical — its position was first contested by the less expensive and more convenient 16 mm. silent motion picture. Later, when the addition of sound revolutionized the film industry, there was little excuse for continuing to produce or use 35 mm. silent films. The principal use of 35 mm. silent films today is by those who have older projection equipment in usable condition and who have a supply of films available at low cost.
One of the newest developments, the 2" x 2" slide, is now making rapid strides as a teaching aid. The majority of these slides are produced by placing 1" x 1%" film prints or transparencies between 2" x 2" cover glasses, or in cardboard binders, to hold the film in a fixed position for projection and to protect it from dust and damage. Others are produced by printing on emulsion-coated glass — as the