Vocabulary for the Common Core. Robert J. Marzano

4, p. 3, italics added)

      As seen in the NRP’s report and echoed by the authors of the CCSS, “the importance of students acquiring a rich and varied vocabulary cannot be overstated” (NGA & CCSSO, 2010a, p. 32).

Vocabulary and Independent Reading

      A large vocabulary helps children learn to read; because of the connections between vocabulary and reading comprehension, students with large vocabularies are more successful readers and therefore more likely to read independently than students with smaller vocabularies. Steven Stahl (1999) described how this relationship affects the amount of reading that students do as they progress through school:

      Because poor readers tend to read less than better readers, the gap between good and poor readers in absolute numbers of words read becomes progressively greater as the child advances through school…. Children who are good readers become better readers because they read more and also more challenging texts, but poor readers get relatively worse because they read less and also less challenging texts. Indeed, researchers have found large differences in the amount of free reading that good and poor readers do in and out of the school. (p. 12)

      In other words, students who read well tend to read more, thus improving their vocabularies and reading skills, while students who have trouble reading tend to read less, thus missing opportunities to augment their vocabularies and improve their reading skills through practice. Much additional research supports the correlation between vocabulary level and reading comprehension (for example, Coyne, Capozzoli-Oldham, & Simmons, 2012; Cromley & Azevedo, 2007; Lesaux & Kieffer, 2010; Stahl & Nagy, 2006). In sum, the effects of vocabulary knowledge on reading comprehension and skill are significant and long lasting.

      Vocabulary and Mental Processes

      Vocabulary is also related to basic mental processes and skills that affect students’ overall academic achievement. Katherine Stahl and Steven Stahl (2012) explained that “children’s ability to name things establishes their ability to form categories” (p. 72). For example, a student who learns the word shake can subsequently attach other words and concepts to it, such as shiver, vibrate, wiggle, flutter, jitter, and so on. As students develop more complex categorization systems for new words, they are better able to summarize (Kintsch, 1998; Kintsch & van Dijk, 1978) and make inferences (Anderson & Pearson, 1984) about new information. Stahl and Stahl (2012) concluded that “to expand a child’s vocabulary is to teach that child to think about the world, and in a reciprocal fashion, [a] more refined vocabulary indicates that child’s degree of knowledge about his or her world” (p. 73). Essentially, knowing more words allows students to think about more concepts in more ways.

      Researchers have also found that there is a significant correlation between vocabulary and intelligence. Joseph Jenkins, Marcy Stein, and Katherine Wysocki (1984) cited correlations as high as 0.80 between vocabulary and intelligence, and Marzano (2004) summarized similarly high correlations between vocabulary knowledge and intelligence, as shown in table 1.2.

Table 1.2: Correlations Between Vocabulary and Intelligence in Various Studies

Study	Correlation
Terman (1918)	0.91
Mahan and Whitmer (1936)	0.87
Spache (1943)	0.92
Elwood (1939)	0.98
McNemar (1942)	0.86
Lewinski (1948)	0.82
Wechsler (1949)	0.78
Raven (1948)	0.93

      Source: Marzano, 2004, p. 32.

      To interpret the correlations in table 1.2, keep in mind that a perfect positive relationship between two variables is indicated by a correlation of 1.00. As one variable increases, so does the other. Therefore, correlations approaching 1.00 (such as those shown in table 1.2) are considered quite strong.

      There are several possible reasons for the correlation between vocabulary and intelligence. First, Stahl (1999) suggested that students who have higher general ability (or intelligence) are simply better at more things, including learning new vocabulary words. Alternatively, Sternberg (1987) postulated that students with higher intelligence learn better from context, and so soak up more words as they encounter various situations. However, it is also possible that students with larger vocabularies can understand more information and therefore analyze information more effectively, thus allowing them to perform better on intelligence tests. A study by Brent Berlin and Paul Kay (1999) illustrates this principle. Berlin and Kay investigated different cultures’ perceptions of color. They discovered that some cultures had fewer terms for colors than others. For example, some cultures only had color terms for light and dark; others for light, dark, and red; others for light, dark, red, and green; and so on. The vocabulary for color in a culture’s language affected their ability to talk and think about the concept of color. In the same way, it is difficult for a student to think about a concept if he or she doesn’t know the word for it. One final explanation for the correlation between vocabulary knowledge and intelligence may have to do with the use of vocabulary-based tasks on intelligence tests. If an intelligence test asks a student to select the appropriate use of a specific word, the student’s success with that task is directly related to his or her knowledge of that word. Whatever the reason for the correlation between vocabulary and intelligence, Stahl and Nagy’s (2006) statement holds true: “Words divide the world; the more words we have, the more complex ways we can think about the world” (p. 5).

The Effects of Vocabulary Instruction

      Given the importance of vocabulary knowledge to academic success, one might assume that vocabulary instruction is of primary importance in most schools. However, Marzano (2004) reported that “uniform and systematic vocabulary instruction is scarce in U.S. schools” (p. 62), citing previous researchers (Durkin, 1979; Roser & Juel, 1982) who found that vocabulary instruction consumed less than one-half of one percent of instructional time in schools. The authors of the CCSS bemoaned the fact that “vocabulary instruction has been neither frequent nor systematic in most schools” (NGA & CCSSO, 2010a, p. 32) and cited a number of research studies (Biemiller, 2001; Durkin, 1979; Lesaux, Kieffer, Faller, & Kelley, 2010; Scott & Nagy, 1997) to support their assertion.

      A number of meta-analyses have examined the effects of vocabulary instruction and intervention on students’ comprehension, oral language, and print knowledge. A meta-analysis is a statistical technique that compiles a large number of studies on a specific topic or instructional strategy (such as direct vocabulary instruction) in order to compute the average effect for that strategy. In other words, a meta-analysis seeks to quantify the overall effectiveness of a given strategy across a number of studies. This effectiveness is often reported using a number called an effect size. In educational research, effect sizes around 0.15–0.20 are considered small, 0.45–0.50 are considered medium, and 0.80–0.90 are considered large (Cohen, 1988; Lipsey, 1990). The higher the effect size, the more effective the strategy.

      Effect sizes are interpreted differently from correlations (discussed previously) because effect sizes commonly represent a student’s expected improvement if they are exposed to a specific strategy. Correlations simply describe the relationship between two variables. So, as illustrated previously in table 1.2 (page 8), intelligence and vocabulary