the psychology of learning and motivation - Percepts and Concepts ...

86 Richard E. MayerRosenthal, Rosnow, & Rubin, 2000). For example, using the data from theprevious paragraph, d = (8.0 6.4)/2.0 = 0.8. According to Cohen, effectsizes of 0.8 or greater are considered large effects and those below 0.2 arenegligible. Hattie (2009) suggests that any effect size above d =0.4ispractically important for education, and notes that effect size gauges thepractical significance of instructional effects rather than simply the statisticalsignificance. Effect size is useful for educational research on instructionaleffectiveness because it provides a common metric for all experimentalcomparisons involving the same independent variable, and is particularlyuseful for meta-analyses in which the effect sizes are averaged across allavailable experimental comparisons (Hattie, 2009).It is important to note that there may be boundary conditions forvarious multimedia instructional methods such that they work best forcertain kinds of learners (e.g., low- versus high-knowledge learners),certain kinds of instructional objectives (e.g., science concepts versusarithmetic procedures), certain kinds of dependent measures (e.g., transferversus retention), and certain kinds of learning environments (e.g., computer-pacedversus learner-paced; Mayer, 2009). Thus, research oninstructional effectiveness should be broadened to examine what worksfor which kinds of learners, learning which kinds of material, based onwhich kinds of measures, and in which kinds of learning environments.3.3. Individual differences in learningConsider the role of learner characteristics in evaluating the effectivenessof multimedia instructional methods, such as the learner’s prior knowledgeor the learner’s cognitive style. With respect to prior knowledge,Kalyuga (2005) has reported the expertise reversal e¡ect for multimediainstructional methods in which multimedia instructional methods thatare effective for low-knowledge learners are not effective for high-knowledgelearners, and in some cases are even detrimental to high-knowledgelearners. For example, Mayer and Gallini (1990) found that adding graphicsto text greatly improved the transfer test performance in lessons onhow various mechanical devices work for low prior knowledge learnersbut not for high prior knowledge learners. Apparently, the high-knowledgelearners were able to mentally build their own images based on thetext whereas the low-knowledge learners needed the instructor’s help.In contrast, Pashler, McDaniel, Rowher, and Bjork (2009) report thatresearch on cognitivestyle—learners’ preferred mode for processing information—hasnot produced reliable attributextreatmentinteractions (ATIs) inwhich one instructional method is better for students with one kind ofcognitive style and a different instructional method is better for studentswith a different cognitive style. For example, Massa and Mayer (2006)asked visualizers and verbalizers to learn from a multimedia lesson on