The utility of the PND statistic: a reply to Allison and Gorman.

Quantitative synthesis ("meta-analysis") of single-subject research has rarely been conducted, partly because of a lack of agreement on how study outcomes are to be quantified. This article provides a response to Allison and Gorman (Behaviour Research and Therapy, 31, 621-631, 1993), who listed some problematic characteristics of use of the PND (percent of non-overlapping data) statistic for computing single-subject study outcomes, and recommended a regression-based solution to computation of effect sizes from single-subject research reports. Although Allison and Gorman are generally accurate in pointing out some limitations of the use of the PND statistic, they have been less thorough in identifying its relative strengths. Among these strengths is the fact that the PND statistic and its variations (a) have been shown to be strongly related to qualitative, "expert" ratings, (b) have been successfully employed in at least seven separate integrative reviews, and (c) have produced results which are complementary to more qualitative reviews of the same literature. In contrast, Allison and Gorman did not report results of applications of their procedure and, although their procedure has apparent theoretical support, it may be less useful in synthesizing existing single-subject literature.

Summarizing single-subject research. Issues and applications.

In this article, literature concerning the quantitative synthesis (meta-analysis) of single subject research literature is reviewed. First, the general rationale for such an approach is discussed. Next, procedures for synthesizing single-subject literature are described, followed by comments and critiques of those procedures. Finally, a review is presented of the results of applications of those procedures. The authors suggest that procedures based on percentage of nonoverlapping data (PND) between baseline and treatment are justifiable, meaningful, and--across nine applications--have produced results that are highly meaningful and faithful to the original research reports.

What happens during instruction: is any metaphor necessary?

This article provides a response to Stone's review and analysis of the scaffolding metaphor as it is applied to research applications for students with learning disabilities. We propose that, to advance the field of instructional research with students with learning disabilities, all available literature should be used when interpreting findings for instructional procedures for students with learning disabilities. Only when all of the intervention research literature in learning disabilities is examined can reliable conclusions be drawn regarding the efficacy of instructional procedures.

Teaching abstract vocabulary with the keyword method: effects on recall and comprehension.

Twenty-five adolescents with learning disabilities were randomly assigned to either a keyword mnemonic condition or an experimenter-directed rehearsal condition and were individually taught 16 difficult vocabulary words, including 8 concrete and 8 abstract words. After an instructional period, students were given a test of literal recall as well as a comprehension test of their ability to apply newly acquired vocabulary words in a different context. Results indicated that mnemonically trained students outperformed control students on both abstract and concrete words, and on recall tests as well as on comprehension tests. Implications for vocabulary instruction as well as theories of learning disabilities are discussed.

Classroom applications of mnemonic instruction: acquisition, maintenance, and generalization.

This investigation evaluated the effectiveness of classroom mnemonic instruction of science content, for 19 students with mild disabilities. Students were given either mnemonic instruction or more traditional instruction in a within-subjects design, in which treatment order was counterbalanced across classrooms, for each of two weekly units in life science. Following a third week of mnemonic instruction, students were taught to generate and draw their own mnemonic pictures. Results suggested that mnemonic instruction resulted in substantial increases in initial content acquisition, and substantially higher delayed-recall scores, over more traditional instructional procedures. Further, it was found that trained students were able to successfully generate and apply their own mnemonic strategies to novel content. Students overwhelmingly preferred mnemonic instruction over traditional instructional methods.

Reading comprehension instruction: summarization and self-monitoring training for students with learning disabilities.

Forty-five middle-school students with learning disabilities were randomly assigned to one of three reading-comprehension training conditions: (a) summarization training, (b) summarization training with a self-monitoring component, or (c) traditional instruction. All students were interviewed before and after training regarding the strategies they typically employ during reading comprehension; during one training session, "think aloud" protocols were collected. Results indicated that students with learning disabilities trained in summarization procedures performed statistically higher on all dependent measures. In addition, on some transfer measures, students who were trained in the monitoring component statistically outperformed those with only the summarization training.

Attitudes of behaviorally disordered students toward tests: a replication.

48 behaviorally disordered and 48 more average students were administered a test attitude survey immediately after district-wide standardized achievement testing. Results were consistent with previous research which suggested behaviorally disordered students may report poorer attitudes than their more typical peers.

Attitudes of behaviorally disordered students toward tests.

In two studies, attitudes reported toward testing by behaviorally disordered students and their regular classroom counterparts were compared. In Study 1, 12 behaviorally disordered and 25 average fifth and sixth graders were given a survey regarding their attitude toward tests and the test-taking experience. Students classified behaviorally disordered reported less positive attitudes toward tests than their more average peers; these attitude differences were more pronounced on items which reflected subjective attitudes toward the test-taking situation and aspirations about performance and less pronounced on evaluation of the value of tests. In Study 2, which employed a sample of 25 behaviorally disordered and 25 regular classroom students matched on age and sex and used a longer attitude measure, differences were not found. Taken together, these studies suggest that attitudes toward tests are inconsistent in the two populations and that some behaviorally disordered students may not differ so much in this regard as supposed.

Stability of whole vs part perceptions of visual stimuli.

In two experiments, college undergraduates (ns = 29, 30) were asked to describe in writing two different abstract line drawings. Responses were classified by over-all orientation to the whole or the individual parts of each drawing. Although findings of the two experiments were very similar, analysis indicated that no strong reliability of orientation existed across the two drawings.

Vocabulary acquisition by mentally retarded students under direct and mnemonic instruction.

Twenty EMR junior-high-school students learned the definitions of unfamiliar English vocabulary words under either direct instruction or mnemonic instruction in a crossover design. When in the mnemonic-instruction condition, students remembered 50% more vocabulary definitions than when they were in the direct-instruction condition. Only three of the 20 students failed to exhibit superior performance when in the mnemonic instruction condition. Supplementary analysis of the response data revealed distinctly different error patterns in the two instructional conditions. In particular, far more intralist intrusions were associated with direct instruction. Implications of these results were discussed.