The use of manipulatives to teach mathematics is often prescribed as an efficacious teaching strategy. To examine the empirical evidence regarding the use of manipulatives during mathematics instruction, we conducted a systematic search of the literature. This search identified 55 studies that compared instruction with manipulatives to a control condition where math instruction was provided with only abstract math symbols. The sample of studies included students from kindergarten to college level (N ϭ 7,237). Statistically significant results were identified with small to moderate effect sizes, as measured by Cohen's d, in favor of the use of manipulatives when compared with instruction that only used abstract math symbols. However, the relationship between teaching mathematics with concrete manipulatives and student learning was moderated by both instructional and methodological characteristics of the studies. Additionally, separate analyses conducted for specific learning outcomes of retention (k ϭ 53, N ϭ 7,140), problem solving (k ϭ 9, N ϭ 477), transfer (k ϭ 13, N ϭ 3,453), and justification (k ϭ 2, N ϭ 109) revealed moderate to large effects on retention and small effects on problem solving, transfer, and justification in favor of using manipulatives over abstract math symbols.

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The present study examined babies as death anxiety buffers with Chinese participants in three experiments. In Experiment 1, death-related thoughts increased college-aged participants' interest in human babies. In Experiment 2, images of newborn animals reduced the number of death-related thoughts recorded by college-aged participants. In Experiment 3, female factory workers who read news articles describing deaths of babies had pessimistic estimations of their own life expectancies. An explanation of these results is provided within a terror management theory framework, with a primary focus on how babies reinforce cultural worldviews and enhance self-esteem via the notion of symbolic immortality. Thus, the anxiety-buffering function of baby is subsumed under cultural worldviews validation and self-esteem enhancement.

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A prescriptive statement is a recommendation that, if a course of action is taken, then a desirable outcome will likely occur. For example, in reading research recommending that teachers apply an intervention targeted at a specific reading skill to improve children's reading performance is a prescriptive statement. In our view, these statements require thorough scientific understanding of causal relationships that follow from scientifically credible research and are generalizable across varied contexts. In this article, we consider both epistemological issues and research credibility indicators (i.e., internal and external validity issues) that restrict one's ability to make prescriptive statements. After presenting an argument for why prescriptive statements should be made sparingly, we describe a stage model of programmatic educational intervention research that is analogous to medical research's phase model and which emphasizes the importance of including appropriate comparison groups, observing replicated findings across different populations and situational contexts, demonstrating statistical relationships between interventions and outcomes, accounting for and ruling out potential alternative explanations for obtained effects, and ultimately conducting randomized field trials. We conclude with the prescriptive statement that only after achieving these high standards of research credibility should educational researchers offer prescriptive statements.Prescriptive statements are consumer-directed recommendations that follow the pattern, "If persons take Action X, then Situation Y will improve" (Robinson et al. 2007;Shaw et al. 2010). 1 These statements are comparable to a doctor saying, "If you take amoxicillin, then Educ Psychol Rev (2011) 23:197-206