There is nothing like acquiring the title of "doctor" to impress elderly relatives. And PhDs remain a rite of passage for many academic careers. Although it is widely agreed that they have changed significantly over the past decade or so, it is far less clear what this means.

There is little doubt that the process of doing a PhD is much more disciplined than it once was. This is all to the good, of course, but it leaves unasked some even more fundamental questions. Have British PhDs changed in terms of content, scope or level of intellectual demand? Have they retained their value, particularly for those seeking work in the international marketplace? And, quite simply, do we still know what a PhD is for?

Janet Metcalfe, chair and head of the organisation Vitae (see box, below right), takes a positive view of what has been happening. Yet even she admits: "There are big issues about what a PhD is for - I personally see them as generic rather than vocational. A finite timescale means you need an achievable project - a piece of research that demonstrates you are a competent researcher."

This, argues Metcalfe, fits in well with the conclusions of the final Bologna doctoral conference, which took place in 2006 and stressed "the uniqueness of the doctoral cycle that provides training by and for research and is focused on the advancement of knowledge".

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The combination of "training for research" and "the advancement of knowledge" is reflected in the Quality Assurance Agency's "doctoral-level descriptors". These state that "doctorates are awarded to students who have demonstrated", among other things, "a detailed understanding of applicable techniques for research and advanced academic inquiry", and "the creation and interpretation of new knowledge ... of a quality to satisfy peer review, extend the forefront of the discipline and merit publication".

Is there perhaps a certain tension embodied in these diverse aims? If PhDs are about both "training for research" and carrying out a particular important research project, one might still ask how the balance should be struck.

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A woman receiving her doctorate was once sent a congratulatory card by a friend that read: "One small step for mankind, but a big one for you." PhDs can certainly provide individuals with the keys to a career in a university or elsewhere.

These can be the specific requirements - laboratory techniques or a publication record - that they will need in academia. Or they may be the intellectual training and generic competencies they will later apply to work in industry, finance or consultancy.

But, beyond imparting specific and more general skills, how many PhDs genuinely contribute to the sum of human knowledge? Many go completely unread. There is a story about someone who put a $100 bill inside his thesis in the university library - and found it, still there, 20 years later.

A related issue was vividly set out by Aberystwyth University academic Peter Barry in his article in last week's ³ÉÈËVRÊÓƵ. Particularly in the humanities, there are genuinely different philosophies of the purpose of postgraduate work - reflected in the mission statements of different funding bodies. Barry playfully calls them the Ivory Tower and Shopping Mall models.

The former is promoted by the research assessment exercise (and its successor, the research excellence framework) and stresses "pure academic excellence", as judged by peers, and the ideal of producing "a contribution of which every researcher in the field ought to be aware".

For the Arts and Humanities Research Council, by contrast, the ideal is research that is "widely disseminated" and researchers who are committed to "interaction with other audiences". Both these goals are valuable, but they clearly put different pressures on PhDs and other research projects.

All this may sound somewhat theoretical, but it leads to a question that has urgent practical implications for individual researchers, universities and even the nation's intellectual capital: how have the changes in the processes affected the contents, international "value" and "fitness for purpose" of British PhDs?

When Sir Gareth Roberts was examining the research assessment exercise, he made a point of urging "the research councils to remember that all evaluation mechanisms distort the processes they purport to evaluate". There was a risk, he noted, that as institutions' "understanding of the system becomes more sophisticated, games-playing will undermine the exercise".

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Few would dispute that the RAE has helped stamp out abuses such as "researchers" who never quite got around to publishing any research. But there has been fierce debate on how it has influenced the kind of research that is carried out.

Similar issues apply to PhDs. There is little doubt that there were cases in the past of people putting forward ridiculously vague proposals for doctorates or being hopelessly dilatory about completion dates. So it was obviously desirable to introduce a bit more discipline and rigour into the process. But how far can this be achieved without introducing "distortions" and "games-playing" or eliciting the even more emotive charge of "dumbing down"?

Take the perceptions of Peter Lake, professor of history at Vanderbilt University, who has been based in America for 16 years but who comes back to Britain every summer. Although he stresses that his experience is confined to the humanities and elite American universities, his views remain pretty damning.

"The constraints put on the British PhD," he argues, "make it harder to do really significant work than it used to be, or (than it) is now in the States." When he started his career in the 1970s, Lake admits, the system was "absurdly lax": he embarked on a PhD at the University of Cambridge knowing and saying only that it was going to be about 17th-century religious history.

However, although a more focused approach was required and completion rates are obviously important, today's excessive stress on these points can be at the expense of "producing work that others will want to read", says Lake.

"The more that you insist on tight completion rates and give grants only to people who have a precise sense of what they are going to work on (and often what they are going to find), the more you bias the system towards very predictable outcomes and away from work that makes a significant contribution to the subject.

"The current pressures on the English PhD are not positive. It is misguided to see success largely in terms of completion rates. We need to think more about purpose.

"The best-funded American programmes offer five years' full funding for PhDs, although they often take six or seven years (including two initial years of coursework). People have more leeway in deciding what to work on and projects define themselves as they go along. It is more difficult to change direction in mid-course in Britain."

Lake continues: "There is no line in the sand in America. A really good seven-year thesis is acclaimed; whereas in England a boring thesis completed on time is regarded as a success."

The most immediate result of this can be put in terms of intellectual capital. "I suspect the English stuff is on average less fully realised, less further along, than the American. It is harder, although not impossible, to do really important work in English PhDs than in American ones, though when I started my assumption was rather the reverse."

In his own field, Lake suspects that this has had a general impact. Since English history is "no longer seen as constitutive of American identity" (and Americans are understandably interested in many other parts of the world), one might expect the subject to be increasingly dominated by researchers working in these islands.

Yet Lake continues to see strong American competition and he suspects "it is probably easier to do a significant PhD on English history on the right American programmes than in the UK".

This has two implications. Lake says he would no longer automatically advise American graduate students, as he might have done in the past, to go to Britain, even if their field is English history. This deprives UK universities of some of the talented people who might continue to research and teach here.

And it also means that the relative value of a British PhD on the international market may be in decline. Although exceptional individuals will always stand out, this could clearly affect British job prospects in the US, continental Europe and elsewhere.

Margot Finn, director of the Institute of Advanced Study at the University of Warwick, notes that her institute "has identified early-career scholarship as a phase of the academic life cycle that deserves special attention and investment".

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One worrying issue, at least in "monograph disciplines", is "the reluctance of even university presses to publish scholars' first books", which used to allow them to build a career on the basis of their PhD research. Certain initiatives such as the Studies in History series (published by Boydell & Brewer for the Royal Historical Society) are specifically designed to address this challenge.

More generally, says Finn, "the pressure on students to complete (PhDs) within three years does create real problems, for example, for students working in languages other than English and for students working across disciplines ... For fields that require use of non-English-language sources, there are clear advantages to US and continental systems: it's very difficult indeed for students to pick up requisite languages within the UK funding framework, and this ultimately can limit the kinds of projects that are undertaken."

One possible solution is to extend the length of PhDs. From 2004, PhDs in economics at Finn's own University of Warwick, for example, have taken four years, including a year's coursework that students are examined on. This brings the institution closer into line with some other British and most American providers, thereby making it more competitive to the largely overseas client base. It also provides a bit more flexibility as initial thesis ideas get modified in the early stages.

The problem, however, is that the Economic and Social Research Council provides funding for only three years, leaving students out on a limb in the fourth (although they are not charged fees during the writing-up process). Those without support from family or governments tend to make ends meet by doing teaching or research - often for more senior academics - which are useful experience and look good on CVs.

Nonetheless, says Fiona Brown, research administrator in Warwick's economics department, "funding councils need to address issues of funding over three years".

A final view of the downside of the more streamlined system that now applies to PhDs comes from Kevin Sharpe, professor of Renaissance studies at Queen Mary, University of London. When he examines PhDs today, he says, he "feels a palpable change in quality and depth of work - an average product looks a very different thing from a decade ago".

He puts this down to two main factors: "undergraduate degrees being much dumbed down" and "the draconian requirement (whereby) departments are penalised if people don't finish on time". Although PhDs were always funded for only three years, the completion time at the University of Oxford until well into the 1980s averaged five years. If people start from a lower base and are forced to finish faster, quality inevitably suffers.

The crucial comparison is with the US. In the UK, people generally take one year for a masters and three more for a PhD. In America, the doctoral qualification usually extends over six years - two years of classwork and then four more for the dissertation itself.

Even voluntary classwork can be problematic here. A woman currently working on a PhD reports that, although she is theoretically allowed to sit in on MA classes, it is considered strange and not encouraged.

And, whatever may have been true in the past, according to Sharpe, Britons "no longer start from a more sophisticated base than Americans".

"An obsession with completion rates skews everything. Their paymasters force universities to pressurise students to finish. An insidious completion culture hits you as soon as you pick a topic.

"Supervisors discourage ambitious projects. Only very intelligent people manage to find a way around the system and avoid the lowest common denominator. The rubric for examiners asks if a PhD is 'a reasonable output for three years'. It is hard for young scholars to work on, say, Spanish history because of the need to improve their language skills and work in a foreign archive - so the field of candidates for jobs outside British history is very poor. Given a very tight timetable, anything that aids fast completion is favoured."

The result is both disastrous and largely invisible. "It's a bit like sterling - it doesn't have a huge effect on you here if it drops or rises, but abroad people have a sense of what the currency is worth - and I think it's shifting," says Sharpe.

"People hiring in this country have come up through the English system and won't notice that British PhDs are weaker than before - but (those with) British PhDs will find it hard to get jobs in the US and elsewhere," he adds.

Since the trend in America is to look for people who can study British history within a broader European or global context, which tends to demand wide linguistic expertise, this can create an additional gulf between supply and demand.

Sharpe is well aware that his critique can be attacked as nostalgia for a non-existent golden age. But it also focuses attention on the crucial - and still very contentious - issue of just what PhDs should be for.

VITAL STEPS TO SUPPORT DOCTORAL RESEARCH

The process of studying for a PhD has undoubtedly been streamlined, most recently with the launch of both the revised Concordat to Support the Career Development of Researchers and the organisation Vitae in July this year. Vitae, which is funded by Research Councils UK, describes its central aim as "enhancing the quality and output of the research base ... through supporting the training and development of the next generation of world-class researchers".

So what made such initiatives necessary? What has changed for those doing PhDs - and perhaps made the transition to early-career academic more difficult? Janet Metcalfe, chair and head of Vitae, says: "I'm not sure the transition is any more difficult than before, but now the agenda is out in the open, whereas doctoral researchers were previously a hidden cohort within universities."

Metcalfe stresses that it is by no means easy to get an accurate picture of what is happening in the job market for postdoctorals. The number of people starting PhDs has not changed greatly over the past decade or so (although there has been a notable increase in international students). And about half of them stay on in higher education in various roles, whether research-based, administrative or academic.

But we have little detailed information about their subsequent career paths: it is only now that research by the ³ÉÈËVRÊÓƵ Statistics Agency is beginning to track exactly what has happened to doctorals three years after they graduate.

Yet a number of factors have had a big impact on what it is like to do a PhD. From the early 1990s, the Economic and Social Research Council and other research councils began to put pressure on completion rates (and to take sanctions, where necessary, against supervisors whose students persistently failed to finish).

In the past, people could continue working on a PhD for far too long. The changes introduced by the research councils, suggests Dr Metcalfe, "act as a counterweight to the natural tendency of researchers and their supervisors to feel like 'we're doing great research here. Let's just keep going'. It led to a huge increase in completion rates. Most institutions require an annual progress report. The process is now much more robust".

Equally important were the results of Sir Gareth Roberts' review, SET for Success, published in 2002. This, says Metcalfe, "highlighted the need for doctoral students to prepare for the transition to careers inside and outside academia. Initiatives, such as the UK GRAD Programme, supported by government funding for institutions, helped make them more aware of the competencies they had developed during their research - and better able to express them in terms employers might understand. But it also helped them become better researchers by improving their time- and project-management skills."

One result of the Roberts review was the creation of the RCUK Academic Fellowships Scheme to "provide (some of) the UK's best researchers with a pathway to a permanent academic position".

In the event, this precipitated a culture change and led a number of universities to "create their own schemes analogous to the Academic Fellowships model". Since such alternative provision is now available, RCUK has no plans to award any new fellowships of its own.

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"We have a fantastic model for the UK PhD," concludes Metcalfe. "The personal support for researchers has been transformed over the past ten years. This kind of support was lacking when I was doing my PhD. Now people don't need to struggle alone."