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Although Shannon and Weaver's The Mathematical Theory of Communication has had a profound impact on the development of communication research, few scholars have adapted Shannon's concepts to their research questions. The authors argue that the failure to recognize the difference between the two fundamental orientations in Shannon's theory—the relationship between source and destination and the technical characteristics of transmission channels—has retarded the use of Shannon's concepts, especially his measure of information. Taking care to differentiate between these two aspects of information theory, the authors review the small body of empirical research inspired by Shannon's theory. They find that Shannon's entropy measure is especially useful in the study of human systems because it permits researchers to analyze categorical data using quantitative statistical tools.

American youth are awash in media. They have television sets in their bedrooms, personal computers in their family rooms, and digital music players and cell phones in their backpacks. They spend more time with media than any single activity other than sleeping, with the average American eight- to eighteen-year-old reporting more than six hours of daily media use. The growing phenomenon of "media multitasking"—using several media concurrently—multiplies that figure to eight and a half hours of media exposure daily. Donald Roberts and Ulla Foehr examine how both media use and media exposure vary with demographic factors such as age, race and ethnicity, and household socioeconomic status, and with psychosocial variables such as academic performance and personal adjustment. They note that media exposure begins early, increases until children begin school, drops off briefly, then climbs again to peak at almost eight hours daily among eleven- and twelve-year-olds. Television and video exposure is particularly high among African American youth. Media exposure is negatively related to indicators of socioeconomic status, but that relationship may be diminishing. Media exposure is positively related to risk-taking behaviors and is negatively related to personal adjustment and school performance. Roberts and Foehr also review evidence pointing to the existence of a digital divide—variations in access to personal computers and allied technologies by socioeconomic status and by race and ethnicity. The authors also examine how the recent emergence of digital media such as personal computers, video game consoles, and portable music players, as well as the media multitasking phenomenon they facilitate, has increased young people's exposure to media messages while leaving media use time largely unchanged. Newer media, they point out, are not displacing older media but are being used in concert with them. The authors note which young people are more or less likely to use several media concurrently and which media are more or less likely to be paired with various other media. They argue that one implication of such media multitasking is the need to reconceptualize "media exposure."

Children four through eleven years old viewed informational (excerpts from network news), persuasive (child-oriented and adult-oriented commercials), educational (excerpts from instructional spots), and mixed (child-oriented public service announcements) messages. They were then interviewed about message content, type, intent, believability, and belief criteria. Comprehension of narrative content was high, even among the youngest children. Most young children were able to identify messages for which common labels exist (news; commercials), but few attached labels to educational spots or public service announcements. Correct articulation of message intent occurred primarily among older children; few under age eight correctly identified the intent of any message type. There was an age-related trend toward the use of functional cues to aid in message identification, and toward reality testing as the appropriate basis for evaluation of message believability. The evidence indicates that young children may interpret messages in informational terms regardless of message intent (e.g., to persuade or instruct).

The relationship between TV use and reading achievemet is reappraised, using data from a 3-year panel study. Strong and significant bivariate correlations replicate the findings of previous studies and support the contention that television use is negatively associated with reading achievement. As increasingly sophisticated analytic techniques are applied to the data, however, the relationships are seen to become progressively weaker, more ambiguous, and less compelling. When the LISREL model is used to tease apart the effects of true change from unreliability in the measures and to account for the stability of the variables over time, three patterns become apparent. First, all three variables of interest in this 3-year panel study−reading skills, TV viewing time, and reading time−are highly intercorrelated at the outset. Second, each of the three variables remains highly stable over the entire period of the study; relatively little variance in our sample measures appears to reflect true change. Finally, what change there is in reading time or in reading skills does not seem to be related consistently to time spent viewing television. Nor does time spent reading nonschool materials seem to predict increases in reading skills to any great extent. It is suggested that the entire question of the influence of out-of-school media use on reading achievement requires a far more sophisticated approach than has been typically applied in the past.

Cluster analysis based on the co-occurrence of key words in letters to national magazines yields qualitative indicators of the public's concerns and breaks new ground in content (and historical) research.

A field study (627 children and 486 of their parents) tests the effects of family communication environment and parental mediation of television content on third-, sixth-, and ninth-graders' perceptions of the realism of television content and its similarity to real life and their identification with television characters. Interpersonal family communication helps children form real-world perceptions, which children intrapersonally compare with their perceptions of the television world better to assess realism. A mismatch between real-world and television-world perceptions diminishes perceptions of realism. Realism contributes to perceived similarity, which contributes to identification with television characters. Through active discussion of television content, the parent directly mediates perceptions of similarity, but not of realism.

This study addresses continuing concern over television's displacement of other leisure activities form both substantive and methodological perspectives. It examines past conceptualizations of the mechanism by which television is assumed to displace other activities. Following a critical review of the displacement literature, the authors examine data from an 8-year panel study of the introduction of television to South Africa and use a variety of methodological approaches to illustrate a major source of inconsistency in findings from previous studies. The displacement mechanism is found to be asymmetric in nature; that is, although increases in television viewing force out some other activities, decreases in television viewing do not result in parallel increases in levels of any of these activities. This pattern of findings was most pronounced in the case of radio use and movie attendance. Implications for conceptualization of the displacement process are discussed in relation to these findings.

"One important element necessary for understanding the role of mass media in the lives of young people is an accurate mapping of their patterns of media use. How much do they use media and which media content, and under what circumstances? This book reports [on a] national random sample survey of U.S. children's and adolescents' use of all of the various media available to them"--Page [i]