Role-play is an unavoidable component of social life, practised with panache by some adults and greatly enjoyed by almost all children. Portraiture exemplifies this. Confronted with a camera, nine people out of ten will adjust their appearance to some preferred image.

Given the slower medium of painting, much more considered effects are employed as can easily be seen in the sometimes subtle, more often blatant posing and play acting of the portraits in this year’s BP Portrait Award exhibition at the National Portrait Gallery. In a pertinent and interactive way, Put Yourself in the Picture, at the same gallery, also engages this impulse.

Taking five 17th-century paintings from the National Portrait Gallery’s collection, children with their parents or teachers are invited to use various props, all reconstructed from the actual pictures, to devise their own compositions and explore the many different levels on which portraits function. Individual choice is crucial. Trying on different masks changing the setting or varying the accessories will reveal just how many alterations of meaning are possible. Deciding which particular permutation suits them best will prompt each participant to reflect on the decisions made by artists and sitters in the selected portraits.

Running through the exhibition are the words of Samuel Pepys recounting his experiences during the painting of his portrait (on show upstairs) by John Hales. Pepys’s manipulation of his own image apparently went little further than the hiring of “an Indian gown” and the choice of a plain sky rather than a distracting landscape as background, but participants will discover in the notes accompanying each portrait that the Duchess of Cleveland substituted fiction for fact. The mistress of Charles II, she appears here as a shepherdess with flowering myrtle, the symbol of marital fidelity. Elsewhere, she posed as the Madonna with one of her several illegitimate children as the infant Christ.

In each section of the exhibition there is a portrait, a full length mirror, some props and a few leading questions with suggested activities. These gently guide participants through the important matters of facial expression, background setting, accessories, costume, pose and overall composition. Ideally, each small group of participants should be able to work alone but if additional support is needed, people are on hand to help.

All the enablers have had some gallery or museum experience and all were involved in the trial runs for the project earlier in the year. The reactions of participants then were enthusiastic. While a six year-old wanted more objects to hold and a 13-year-old suggested thought bubbles, a 12-year-old girl found it “easy to read and understand, so I think it works well.”

An evaluation of the project will be done by Professor John K Gilbert of the University of Reading and Dr Mary Priest of Linkages Educational Consultants and published by the university.

Put Yourself In The Picture, until October 29. BP Portrait Award 1995, until October 15. Free admission to both. For further information and special arrangements for school visits, telephone the National Portrait Gallery Education Department 0171 306 0055.