Reading Volume and
Declarative Knowledge
In other studies, we have focused even more directly on content knowledge by addressing the issue of “Where Does Knowledge Come From?”. Stanovich and Cunningham (1993) examined general ability, reading volume, and exposure to other media sources as determinants of individual differences in content knowledge. This study contained a particularly stringent test of the role of reading volume and individual differences in knowledge acquisition among 268 college students. We administered five different measures of general knowledge to the students. Then we stacked the deck against reading volume once again by statistically entering four measures of general ability before looking at the contribution of reading volume: high school grade-point average, performance on an intelligence test, an SAT-type mathematics test, and an adult reading comprehension test. This set of tasks surely exhausts the variance attributable to any general ability construct; and, as one would expect, we found that general ability accounted for a substantial proportion of variance in the composite measure of general knowledge. Next we entered a composite measure of exposure to television, but it did not account for any additional variance. However, a composite index of reading volume accounted for a substantial 37.1 percent of the variance when entered after the four ability measures and television exposure.
This pattern was replicated in each of the five measures of general knowledge we employed, including a homemade instrument we called the Practical Knowledge Test. This task was designed to address the criticism that our other measures of general knowledge were too academic— that they tapped knowledge that was too esoteric or elitist and that was not useful in daily life. We didn’t think this was true; many items on these measures were mundane and concrete questions such as “In what part of the body does the infection called pneumonia occur?” Nevertheless, in the Practical Knowledge Test, we made an effort to devise questions that were directly relevant to daily living in a technological society in the late twentieth century; for example, What does the carburetor in an automobile do? If a substance is carcinogenic, it means that it is? After the Federal Reserve Board raises the prime lending rate, the interest that you will be asked to pay on a car loan will generally increase/decrease/ stay the same? What vitamin is highly concentrated in citrus fruits? When a stock exchange is in a “bear market,” what is happening? and so forth.
The results indicated that the more avid readers in our study—regardless of their general abilities— knew more about how a carburetor worked, were more likely to know who their United States senators were, more likely to know how many teaspoons are equivalent to one tablespoon, were more likely to know what a stroke was, and what a closed shop in a factory was, etc. One would be hard pressed to deny that at least some of this knowledge is relevant to living in the United States in the late 20th century.
In other questions asked of these same students, we attempted to probe areas that we thought might be characterized by misinformation. We then attempted to trace the “cognitive anatomy” of this misinformation. One such question concerned the sizes of the world’s major religions and was designed to assess awareness of the multicultural nature of the modern world. The question was phrased as follows: “The 1986 Encyclopedia Britannica estimates that there are approximately nine hundred million people in the world (not just the United States) who identify themselves as Christians. How many people in the world (not just the United States) do you think identify themselves as ?” Space was then provided on the form for the subjects to make estimates of the number of Moslems, Jews, Buddhists, Hindus, etc.
We will focus here on the estimates of Moslem and Jewish people because of our a priori hypothesis that availability effects caused by televised coverage of Israel in the U.S. had skewed the perception of this ratio. While our sample’s median estimate of the number of Jewish people (20 million) was quite close to the actual figure of 18 million according to the 1990 Universal Almanac, the number of estimated Moslems—a mean of 10 million—was startlingly low (817 million is the estimate in the Universal Almanac). For each participant in our study, we calculated the ratio of the Moslem to Jewish estimates to see how many students were aware of the fact that the number of Moslems is an order of magnitude larger (the actual estimated ratio is approximately 33:1 according to the World Almanac; 45:1 according to the Universal Almanac). The median ratio in our sample was 0.5. That is, 69.3 percent of our sample thought that there were more Jewish people in the world than Moslems. This level of inaccuracy is startling given that approximately 40 percent of our sample of 268 students were attending one of the most selective public institutions of higher education in the United States (the University of California, Berkeley). We have explored the correlates of this particular misconception in a variety of ways. We looked at the performance on this question as a function of students’ level of reading volume and television watching. We observed a clear effect of reading volume on the scores on the question and a significant effect of television viewing, but the effects were in opposite directions! Reading volume was associated with higher scores on the question, but television exposure was associated with lower scores. Scores among the group high in reading volume and low in television exposure were highest, and the lowest scores were achieved by those high in television exposure and low in reading volume. Our analyses confirmed that these relationships were not due to differences in general ability.
Similarly, we have analyzed a variety of other misconceptions in a number of other different domains—including knowledge of World War II, the world’s languages, and the components of the federal budget—and all of them replicate the pattern shown for this question. The cognitive anatomy of misinformation appears to be one of too little exposure to print (or reading) and over-reliance on television for information about the world. Although television viewing can have positive associations with knowledge when the viewing is confined to public television, news, and/or documentary material (Hall, Chiarello, & Edmondson, 1996; West & Stanovich, 1991; West et al., 1993), familiarity with the prime time television material that defines mass viewing in North America is most often negatively associated with knowledge acquisition.
In another study, Stanovich, West, & Harrison (1995) examined a much older population in order to investigate the extent to which age-related growth in knowledge can be accounted for by differences in reading volume. Although much research effort has been expended on describing cumulative growth in crystallized intelligence (e.g., acquired knowledge such as vocabulary and general information), we know little about the experiences that relate to knowledge growth in older individuals. For example, educational experience (years in school) is a predictor of intellectual functioning in older individuals (e.g., Schwartzman, Gold, Andres, Arbuckle, & Chaikelson, 1987). It is assumed that education (which is received early in life) in part determines the extent and quality of many intellectual activities later in life. And it is presumably this intellectual activity as one ages that is so crucial to the preservation of cognitive capacities. Thus, while considerable development of cognitive skills and abilities can result from formal educational experiences, it is the lifetime use of these skills that is assumed to have the beneficial effect.
In this study, Stanovich, et al. (1995) examined the performance of college students and senior citizens on general knowledge, vocabulary, working memory, syllogistic reasoning, and several measures of reading volume. The older individuals outperformed the college students on the measures of general knowledge and vocabulary, but did significantly less well than the college subjects on the working memory and syllogistic reasoning tasks. This dissociation between fluid intelligence (all-purpose general problem-solving capacity) and crystallized intelligence (general knowledge and vocabulary) is a standard finding in the literature (Baltes, 1987; Horn & Hofer, 1992; Salthouse, 1988). However, a series of analyses indicated that when measures of reading volume were used as control variables, the positive relationships between age and vocabulary and age and declarative knowledge were eliminated (in contrast, the negative relationships between age and fluid abilities were largely unchanged). Thus, the results of this study are consistent with the conjecture that—in the domain of verbal abilities—reading a lot can even help to compensate for the normally deleterious effects of aging! (See also, Smith, 1996.)
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