Now comes another skirmish in the generation wars, the fight about whether post-boomers are selfish, moneygrubbing fame-seekers — the “Me” Generation — or confident, group-oriented volunteers — the “We” Generation.

The latest salvo comes from Jean Twenge, a psychologist at San Diego State University and author of “Generation Me and the Narcissism Epidemic.” She’s still critical of her own generation, the Generation Xers born between 1962 and 1981, and the Millennials born after that.

In research published recently in the Journal of Personality and Social Psychology, Twenge found that, over the last 40 years, young people have become increasingly focused on money and fame while caring less about politics, their communities, or the environment. Her team based its conclusions on analyses of surveys taken by 9 million high school seniors and college freshmen.

“I think it’s potentially problematic to have this generational decline in civic engagement and community involvement, and that’s because these are the bedrock of a society,” Twenge said.

Michael Hais and Morley Winograd, authors of “Millennial Momentum: How a New Generation Is Remaking America,” take a more favorable view of the younger generations and were quick to find fault with Twenge’s study.

At 69, the pair are too old even to be boomers, who also were once known as the Me Generation. They said old-fashioned wording of the survey questions may have underestimated modern students’ interest in the environment and community improvement. Hais said surveys that focus on actions rather than attitudes show Millennials “are actually a very participatory generation.”

Twenge downplays survey results showing increased volunteerism because many high schools require it. Hais and Winograd say the volunteering continues into college and young adulthood. They’re not so high on Gen Xers, whom Winograd described as mistrusting and skeptical of both younger and older generations, but compared Millennials favorably to the G.I. Generation that Tom Brokaw labeled the Greatest Generation. These “civic generations” tend to be raised by extremely loving and involved parents.

At Clark University, Jeffrey Jensen Arnett studies “emerging adults,” ages about 18 to 25. He doesn’t think change comes neatly packaged in generations, but said youth trends over the last 20 years have mainly been positive. Volunteerism and graduation rates are up, he said, while crime, drug use, and teen pregnancy are down. Today’s young people are tolerant of differences in ethnicity, sexual orientation, and religion, he said. If anything, he said, this is a “generous generation.”

Twenge said survey questions on what students did, rather than what they thought, supported her view.

You’re part of Generation Me, Twenge said, if you did an “All About Me” project in school and saw posters on the classroom wall that said, “Believe in Yourself” or “Anything Is Possible.”

The biggest drop was in if youths felt the need to develop a meaningful philosophy of life. Seventy-three percent of boomers thought that was important, compared with 45 percent of Millennials, but Millennials still thought it more important than money.