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Violent video games are increasingly popular, raising concerns by parents, researchers, policy makers, and informed citizens about potential harmful effects. Chapter 1 describes the history of violent games and their explosive growth. Chapter 2 discusses research methodologies, how one establishes causality in science, and prior research on violent television, film, and video games. Chapter 3 presents the General Aggression Model, focusing on how media violence increases aggression and violence in both short and long-term contexts. Important scientific questions are answered by three new studies. Chapter 4 reports findings from a laboratory experiment: even children's games with cartoonish violence increased aggression in children and college students. Chapter 5 reports findings from a survey study of high school students: frequent violent game play leads to an angry and hostile personality and to frequent aggression and violence. Chapter 6 reports findings from the first longitudinal study video game effects: elementary school children who frequently played violent games early in the school year became more verbally and physically aggressive, and less helpful. Chapters 7 and 8 compare a host of risk factors for development of aggression, and find video game effects to be quite important. Chapter 9 describes the role of scientific findings in public policy, industry responses to scientific findings, and public policy options. Chapter 10 recommends that public policy debates acknowledge the harmful effects of violent video games on youth, and urges a more productive debate about whether and how modern societies should act.

A dyadic interactive aggression paradigm tested hypotheses from the General Aggression Model about how trait aggressiveness can create behaviorally hostile social environments. Pairs of college student participants competed in a modified reaction time task in which they repeatedly delivered and received each other's punishments. The trait aggressiveness of both participants influenced the punishment intensities (aggression level) set by each member of the dyad on later trials. Furthermore, there was a pattern of escalation from early to later trials. These trait aggressiveness effects (both self and partner) on later aggressive behavior were largely mediated by partner aggression levels during early trials. Results also suggested two aggressive motives--hostile and instrumental--resulted from high partner aggression during early trials and these motives partially mediated the effects of trait aggressiveness and of early trial aggression on later aggressive behavior.

This chapter discusses the magnitude of media violence effects, the idea of media violence providing catharsis (venting) for aggression, and a host of public policy questions. It shows, for example, that the harmful effects of violent video games are at least as large as many other known risk factors, such having abusive parents. Furthermore, video game violence is important because almost all children are exposed to this risk factor. The vast array of media violence studies over the last 50 years strongly disproves the catharsis idea that (unfortunately) remains so popular in modern culture. This is the idea that using violent media allows a person to vent their pent up aggressive inclinations, thereby reducing real aggressive behavior. Although this idea is appealing, it is wrong. The chapter concludes with descriptions of a wide array of public policy options that various concerned parents, legislators, and policy makers in a number of countries have proposed to address the harmful effects of violent video games.

Composting of livestock manure is an effective method for managing the nutrients for agronomic purposes and reducing environmental and human health risks. Capability to analyze the biowastes on-site at the start of, periodically during, and at the end of composting could facilitate managing the composting process and increase the value of the end products. Near-infrared spectroscopy (NIRS) is well known for its capability to analyze organic substances rapidly and cost-effectively. This study was conducted to explore the capability of a field-portable NIR spectrometer to determine nutrient composition of beef feedlot manure when raw, stockpiled (not turned), and composted (windrowed and turned). Over a 2-yr period, beef feedlot manure mixed with bedding (wheat straw) was sampled annually at cleanout, after storage for some months in a large stockpile, and from windrows subjected to active thermophilic composting. Samples were dried and ground and scanned with the field-portable Corona 45 VIS NIR (visible/near-infrared) spectrometer (Carl Zeiss, Germany) from 360 to 1690 nm. NIRS was found useful in two ways. Classification analysis (Soft Independent Modeling of Class Analogy [SIMCA]) using the spectral data alone showed that stockpiling the manure did not change in composition significantly whereas compost was