Undergraduates are being coerced into taking part in psychological experiments, it was claimed this week.
While thousands of psychology students volunteer to be subjects in research projects every year, some universities make participation compulsory.
Richard Nicholson, editor of the Bulletin of Research Ethics, fears this might expose some to risk of psychological harm and could represent a breach of the Nuremberg Code.
These guidelines, drawn up in response to Nazi experimentation on humans, require free, informed consent from each subject.
The principle of "no coercion" is under discussion by a British Psychological Society (BPS) working party that is updating guidelines for best ethical practice in research. The example of Stirling University was brought to Dr Nicholson's attention by concerned members of the Forth Valley National Health Service research ethics committee.
Roger Watt, head of psychology at Stirling, said students were expected to participate in eight experiments in the first two years of study. If someone declined, he said, "then, in principle, the department would be able to refuse entry to honours psychology". He denied this was a breach of the Nuremberg Code as everyone was informed of the nature of the research, could decline to take part and, if they had good reason, they would not be refused a degree.
He said no one had yet chosen to opt out, adding that it was of "paramount importance that students experienced the research process from both sides".
"Any student who might choose not to participate in any form of psychological research on ethical grounds will not be willing to undertake research on the same ethical grounds. Such students will not be able to fulfil degree-course requirementsI,s" he said.
But Dr Nicholson said he found Stirling's practice "troubling". "It sounds a long way from being voluntary. If you want to do the course, you have to do the research," he said.
He argued this was not an appropriate approach for research on human subjects since every experiment carried some risk.
"It is not clear to me that they are working within the Nuremberg Code because it seems to me that there's a hefty amount of coercion here," he said, adding that similar practices were likely to be found in other universities and other disciplines.
Max Velmans, convener of the BPS working party, said participants in research should not be coerced. But he added: "When training research psychologists, there may be a pedagogical need as well as an ethical obligation on them to participate in research." But he said: "Participants should be given alternatives."
Dianne Parker, senior lecturer in psychology at Manchester University, said all first-year psychology undergraduates were asked to participate in 15 hours of research. But if anyone refused, they were assigned to write an extended essay on ethics.
"We see participation in research as part of the learning process, but it is not compulsory," Dr Parker said.