Fresh doubt about the sole authorship of a Shakespearean play has been cast by two scientists from Aston University, Birmingham.

Using pioneering computing techniques, Professor David Lowe and Robert Matthews have concluded that the 350-year-old play, The Two Noble Kinsmen, was the joint work of William Shakespeare and John Fletcher, a gifted young fellow playwright.

"In recent years the consensus has increasingly been that the attribution on the frontispiece can be taken at face value," said Mr Matthews. When the play was published in 1643 it carried the legend "Written by the memorable Worthies of their time Mr John Fletcher and Mr William Shakespeare, Gent".

The two doubting academics, from Aston's neural computing research group, used a powerful form of neural computing, called radial basis functions, in coming to their conclusion.

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They trained a computer to recognise the characteristic styles of Shakespeare and Fletcher by showing it word-frequency patterns from undisputed examples of each playwright's work.

Once it had been trained, the neural computer was tested by being asked to identify other undisputed works by each dramatist. The computer successfully classifed them all.

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It was then put to work on The Two Noble Kinsmen, a play in five acts. It decided that the first and last acts were the work of Shakespeare, but the second appeared to be written by Fletcher. Acts III and IV appeared to be written jointly. This tallies with the findings of literary scholars who have examined more complicated features such as imagery and phrasing. The neural computer looked at the play at a simpler level, comparing the relative frequency that words like "are" and "of" appeared. Such words are used almost subconsciously by writers.

Professor Lowe said: "There is growing interest in using computers to solve literary mysteries, but they have to be used with care. They cannot perform miracles with dubious or inadequate data and they are no more infallible than any human scholar. Used appropriately, however, they can provide literary scholars with a valuable extra source of evidence."