Researchers from Heriot-Watt University's department of accountancy, economics and finance carried out an online survey of postgraduate student teaching activities. About 1,100 students, mostly researchers, responded.
Of the 500 respondents from Scottish institutions, more than 60 per cent were involved in teaching - 84 per cent of those by choice. Typical duties for postgraduate teaching assistants include tutoring, demonstrating and helping with assessment. Around 13 per cent also lectured.
Most of those surveyed taught for up to four hours a week, but a small number taught for more than eight.
"Considering that preparation and teaching hours appear to require a similar number of hours...this could place some research students at a disadvantage," the researchers say in a paper on the Scottish results, "The Role, Responsibilities and Remunerations of Graduate Teaching Assistants in Scotland", currently under review for publication.
The study found a wide variation in pay rates, from ?6 to ?72 an hour. The highest salaries were in law, music, and accounting and finance, with the lowest in sport, physics and bioscience. Training was not universally available and was often generic rather than subject specific.
"This surely needs to be addressed if quality teaching is the goal of HEIs and the main objective of government education policy," the paper says. It predicts that universities will rely increasingly on postgraduates as the research burden on full-time academics increases.
The study expresses particular concern about the 14 per cent of respondents who taught other postgraduates, and warns that those who do not want an academic career and are not interested in teaching could "deliver" that lack of interest to undergraduates.
"This could have a wider impact on student retention rates and reduce the overall quality of the undergraduate experience," it warns.