text: Youth movement This movement represented a shift in the cultural attitudes and perceptions of adulthood in Western cultures. Previous to this movement in the 1960s and 1970s, many young people aspired to grow up and become adults who were considered wise, in control, and independent. Adulthood as a stage was something to desire to achieve. However, the youth movement changed perceptions of adulthood to be less favorable than those of youth. Music and phrases reflected the growing movement to celebrate youth and renounce aging. For example, phrases like "I want to be forever young" and "never trust adults" became increasingly common, and youth began to prevail over wisdom, associated with aging, in terms of popularity. Many youth groups developed at the beginning of the 20th century in several Western countries. One example was the Boy Scouts of America. These youth groups supported the development of the youth movement by idolizing the opportunities and qualities of youth. Because of this idolization of being young, young adults postponed adulthood and prolonged their youth into their twenties by living independently of conditions and characteristics associated with adulthood, like marriage and child-rearing. The delay of adulthood and popularization of remaining young brought about by this revolution led to the development of emerging adulthood. The youth movement, in conjunction with the technology revolution, sexual revolution, and women's movement, were thought to have contributed to the development of emerging adulthood as a stage of life by Arnett.
  Physiological development
  Biological changes
  Emerging adulthood and adolescence differ significantly with regard to puberty and hormonal development. While there is considerable overlap between the onset of puberty and the developmental stage referred to as adolescence, there are considerably fewer hormonal and physical changes taking place in individuals between the ages of 18 and 25. Emerging adults have reached a stage of full hormonal maturity and are fully, physically equipped for sexual reproduction.
  Emerging adulthood is usually thought of as a time of peak physical health and performance as individuals are usually less susceptible to disease and more physically agile during this period than in later stages of adulthood. However, emerging adults are generally more likely to contract sexually transmitted infections, as well as to adopt unhealthy behavioral patterns and lifestyle choices.