Only since the late 1980s has there been sufficient special education research published that meta-analyses and syntheses can be conducted. In this volume, seven sets of authors grapple with synthesizing the knowledge base on an array of critical topics in the field of special education. Anyone who has attempted a meta-analysis or a comprehensive research synthesis is aware of how formidable a task it is. Issues that seem relatively easy or straightforward when described in a textbook are usually extraordinarily intricate and perplexing when put into practice. Every decision, from defining the target population to exclusion criteria for studies, invariably opens up a can of worms. Where one expects many studies, often there are few. And where relatively few are expected, there are often far too many to be able to synthesize properly.
The textbooks oversimplify the meta-analysis process. Meta-analysis and research synthesis involve objective techniques, but the ultimate goal is illumination of the topic at hand. As writers, each of us has faced the problems of discerning--with validity--the underlying patterns in the data, of struggling to articulate what they really mean, and of finding ways to communicate this to others.
The great American poet, Charles Olson, was an admirer of science and technology in an era when it was unfashionable. He wrote eloquently of the gifts we gain from scientific inquiry. But he cautioned:"And the too strong grasping of it, when it is pressed together and condensed, loses it ..." ( Charles Olson, 1966).
Hasn't anyone who has done a meta-analysis or a research synthesis at some point asked herself or himself. "Is that all there is?" Clearly there must be more here, than a series of weighted and unweighted mean effect sizes. The continual struggle is to discern trends that are valid.