But when it comes to “why,” the answers are less clear. The easy culprits — the allure of the Internet (Facebook!), the advent of new technologies (dude, what’s a card catalog?), and the changing demographics of college campuses — don’t appear to be driving the change, Babcock and Marks found. What might be causing it, they suggest, is the growing power of students and professors’ unwillingness to challenge them.

The research, accepted to be published in the Review of Economics and Statistics, has already sparked discussions in faculty lounges and classrooms across the country. Some question whether college students ever could have studied 24 hours a week — roughly three and a half hours a night. But even if you dispute the historical decline, there is still plenty of reason for concern over the state of 21st-century study practices. In survey after survey since 2000, college and high school students are alarmingly candid that they are simply not studying very much at all. Some longtime professors have noted the trend, which rarely gets mentioned by college admissions officials when prospective students visit campus.

“It’s not just limited to bad schools,” Babcock said. “We’re seeing it at liberal arts colleges, doctoral research colleges, masters colleges. Every different type, every different size. It’s just across the spectrum. It’s very robust. This is just a huge change in every category.”

SAT scores of the people enrolled there, the results are the same: Students of all ability levels are studying less.

The decline, Babcock and Marks found, infects students of all demographics. No matter the student’s major, gender, or race, no matter the size of the school or the quality of the

It is a fundamental part of college education: the idea that young people don’t just learn from lectures, but on their own, holed up in the library with books and, perhaps, a trusty yellow highlighter. But new research, conducted by two California economics professors, shows that over the past five decades, the number of hours that the average college student studies each week has been steadily dropping. According to time-use surveys analyzed by professors Philip Babcock, at the University of California Santa Barbara, and Mindy Marks, at the University of California Riverside, the average student at a four-year college in 1961 studied about 24 hours a week. Today’s average student hits the books for just 14 hours.

They come with polished resumes and perfect SAT scores. Their grades are often impeccable. Some elite universities will deny thousands of high school seniors with 4.0 grade point averages in search of an elusive quality that one provost called “intellectual vitality.” The perception is that today’s over-achieving, college-driven kids have it — whatever it is. They’re not just groomed; they’re ready. There’s just one problem.

“Are students just that much more efficient that more than 60 percent of students study less than 15 hours a week and still earn As and Bs?” Kinzie asked. “Or are we really preparing students for the world of work if they’re able to get by spending that many hours studying and preparing for class?”

Once they get to college, the figure improves, but there are many students today who appear to be doing very little whatsoever. In one CIRP survey subset last year, analyzing predominantly private institutions considered to be mid-level or high-achieving colleges, some 32 percent of college freshmen somehow managed to study less than six hours a week — not even an hour a day. Seniors studied only slightly more, with nearly 28 percent studying less than six hours a week. And other surveys of today’s students report similarly alarming results. The National Survey of Student Engagement found in 2009 that 62 percent of college students studied 15 hours a week or less — even as they took home primarily As and Bs on their report cards.

One problem is that they’re arriving in college with increasingly troubled study habits. According to survey data gathered by the Cooperative Institutional Research Program, or CIRP, the largest and longest-running study of higher education in the United States, incoming college freshmen have reported declining study habits for at least two decades. By 2009, nearly two-thirds of them failed to study even six hours a week while seniors in high school — a figure that has risen steadily since 1987.

“So if students are taking a full load of 15 credit hours, they should be studying for 30 hours,” said Jillian Kinzie, the associate director of the National Survey of Student Engagement, a nonprofit at Indiana University. “Clearly, that’s not happening.”

Studying has long been considered a key part of a college student’s growth, both as a means to an end — a deeper understanding of the subject matter — and as a valuable habit in its own right. A person who can self-motivate to learn, academics argue, is not only more likely to be a productive worker, but more fulfilled citizen. As a result, universities for decades have stated — sometimes officially — that for every hour students spend in class each week they are expected to be studying for two hours on their own.

Whatever the reason, one thing is clear: The central bargain of a college education — that students have fairly light classloads because they’re independent enough to be learning outside the classroom — can no longer be taken for granted. And some institutions of higher learning have yet to grapple with, or even accept, the possibility that something dramatic has happened.

But one sign that studying still has value is that students themselves are concerned about it. In a 2008 survey of more than 160,000 undergraduates enrolled in the University of California system, students were asked to list what interferes most with their academic success. Some blamed family responsibilities, some blamed jobs. The second most common obstacle to success, according to the students, was that they were depressed, stressed, or upset. And then came the number one reason, agreed upon by 33 percent of students, who said they struggled with one particular problem “frequently” or “all the time”: They simply did not know how to sit down and study.

Hours spent studying is not the end goal of an education, of course, nor the only way to determine if someone is learning or will land a job after college. Marks herself points out that employers don’t generally care about the content of job applicants’ classes; they’re more interested in whether an applicant graduated, was able to meet deadlines, and work within a bureaucracy.

That’s true, Babcock and Marks agree. But according to their research, the greatest decline in student studying took place before computers swept through colleges: Between 1961 and 1981, study times fell from 24.4 to 16.8 hours per week (and then, ultimately, to 14). Nor do they believe student employment or changing demographics to be the root cause. While they acknowledge that students are working more and campuses attract students who wouldn’t have bothered attending college a generation ago, the researchers point out that study times are dropping for everyone regardless of employment or personal characteristics.

“A student doesn’t need to retype a paper three times before handing it in,” said Heather Rowan-Kenyon, an assistant professor of higher education at Boston College. “And a student today can sit on their bed and go to the library, instead of going to the library and going to the card catalog.”

According to the skeptics of the findings, there is one other notable change: Today’s students are working with more efficient tools when they do finally sit down to study. They don’t have to bang out a term paper on a typewriter; nor do they need to wander the stacks at the library for hours, tracking down some dusty tome.

“Much busier,” Bravman said, describing the “on-demand” world that students work in today. “I was a student here from ’75 to ’79. I was reasonably engaged in things. But I had so much free time compared to students today. They do so many things — it’s amazing.”

John Bravman, vice provost for undergraduate education at Stanford University, said that what he worries about these days is not that students are lazy, but that they are too busy — busier than previous generations of Stanford students.

Critics say it’s misleading to measure today’s students by the number of hours they spend studying. Students live very different lives than they once did. They are more likely to hold down jobs while attending classes.

So what now? Given Babcock and Marks’s findings, what should universities be doing to improve study habits? It’s an answer that depends, first, on understanding why students are studying so little these days. And on this point, there is little agreement.

One theory, offered by Babcock and Marks, suggests that the cause, or at least one of them, is a breakdown in the professor-student relationship. Instead of a dynamic where a professor sets standards and students try to meet them, the more common scenario these days, they suggest, is one in which both sides hope to do as little as possible.

“No one really has an incentive to make a demanding class,” Marks said. “To make a tough assignment, you have to write it, grade it. Kids come into office hours and want help on it. If you make it too hard, they complain. Other than the sheer love for knowledge and the desire to pass it on to the next generation, there is no incentive in the system to encourage effort.”

The problem dates back to the 1960s, said Murray Sperber, a visiting professor in the graduate school of education at the University of California Berkeley. Sperber, at the time, was a graduate student at Berkeley and was part of an upstart movement pushing for students to rate their professors. The idea, Sperber said, was to give students a chance to express their opinions about their classes — a noble thought, but one that has backfired, according to many professors. Course evaluations have created a sort of “nonaggression pact,” Sperber said, where professors — especially ones seeking tenure — go easy on the homework and students, in turn, give glowing course evaluations.

In response to these concerns over course evaluations — and the state of collegiate studying in general — some universities are making changes. Some administrators in recent years have been putting less weight on course evaluations when making tenure decisions. Professors are being told to give explicit tasks to students. Just telling them to read these days is often considered “too generic, too general of a request,” said Kinzie. And many professors today are using Internet-based systems, like Blackboard , where students are required to log on and write about the assigned reading for all of their classmates to see.

Dan Bernstein, director of the Center for Teaching Excellence at Kansas University, said such assignments can help ensure that students are reading and will come prepared for class. But as the Babcock/Marks survey shows, universities aren’t coming close to meeting their own expectations for what should be happening on campus. “That,” said Bernstein, “is one of our dirty little secrets.”

It’s possible that college administrators simply don’t know what’s happening — or rather, not happening — in their dormitories, libraries, and classrooms. The decline in study hours, according to the new research, has happened gradually over decades. Perhaps, some professors argue, colleges simply don’t know the extent of the problem — and perhaps a discussion of the new research will lead to positive changes. But there is also a more troubling reason why the study habits of today’s students remain a discussion held in private, or not at all.

“If we let it be known that they’re not doing their part, that they’re not the students of yore, that makes everybody uncomfortable,” said Bernstein, a professor of psychology who’s been teaching for 35 years. “Our constituents — our stakeholders, as they call them — would be unhappy. They like to prefer that we’re doing our jobs well.”

Freelance writer Keith O’Brien, winner of the Casey Medal for Meritorious Journalism, is a former staff writer for the Globe. E-mail him at keith@keithob.com.

© Copyright 2010 Globe Newspaper Company.