Painting by numbers

One of the staple exercises in statistics education is to make a light hearted foray into that old academic wrangle: were the Shakespeare plays and sonnets really written by William Shakespeare or by [insert your favourite candidate here]? Various metrics are analysed by whatever techniques are being taught, with a view to assessing similarity and difference. Real literary academics, of course, have visited the same methods with serious intent, and similar debates exist within the visual plastic arts. Was this unsigned painting produced by old master X, or by unknown Y?

A very well known example of such a dispute concerns the early 17th century Baroque painter Artemisia Gentileschi. In the last fifty years she has been rehabilitated in art history circles and is now widely recognised, but for centuries much of her work was wrongly attributed to others. The most frequent misattributions were to her father Orazio (which most experts now regard as blatantly ridiculous but which can be blamed on signatures) or to Michelangelo Merisi da Caravaggio who painted in a superficially similar style a generation earlier. Reattribution was in most cases visual by expert witnesses but in a few cases appeal was made to more objective means.

Disputes still occur, however, and as recently as January of this year a bitter disagreement between two national art institutions, with significant financial implications, was finally settled. The process is plastered with nondisclosure clauses, but people love to talk about their interesting cases... [more]

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• Illustration: Artemisia Gentileschi, La Pittura, c1638. Oil on canvas, 986mm × 752mm. Part of The Royal Collection.