Investigators of this study bring together survey data from sources both new and old in order to test the generational hypothesis that national and world events experienced during a "critical period" of later childhood, adolescence, and early adulthood have a disproportionate effect on memories, attitudes, and actions in later life. Also considered were competing explanations for the same evidence, especially interpretations based on period and recency effects. The data come from nine surveys, mostly national, carried out in the United States and in six other countries (China, Germany, Israel, Japan, Lithuania, and Russia), between 1985 and 2010. The hypothesis is largely supported for recall of past events, and also for commemorative behavior connected to World War II and to the Vietnam War. The evidence is mixed with regard to attitudes toward the Gulf War and the Iraq invasion, emphasizing the distinction between generational effects that result from lifetime experience and those due to a critical period. The analysis considered most of the major events faced by Americans over the past 80 years, ranging from the Great Depression to current issues, including such national traumas as the assassination of President Kennedy, the Vietnam War, and the September 11, 2001, terrorist attack. Comparable events in other countries were also examined.