If the face holds the key to first impressions, amateur psychologists should have a field day at this new exhibition at the Scottish National Portrait Gallery.

This wide-ranging exhibition of sculptural portrait heads is full of honesty and dissemblance, familiarity and surprise.The visitor's own first impression to this exhibition of sculptural portrait heads - and sometimes attendant bodies - may be more one of confusion, says Chief Curator and Deputy Director of the Portrait Gallery, Imogen Gibbon, when they are confronted at the door with Jacob Epstein's towering sculpture of The Risen Christ. "I wanted people to ask why this sculpture is a portrait," says Gibbon.

Modelled during the First World War, Epstein's Christ is weary and human, which is no surprise when you find out that the face was a mask modelled from life of his friend, the composer Bernard Van Dieren, as he lay on his sickbed.

"Epstein said when he saw the face he had modelled, he immediately recognized it as the Christ head," explains Gibbon. "A lot of this exhibition is about how sculptors draw out the portrait from the process of working and modelling the head."

If Epstein's portrait speaks of the loss of war, and perhaps particularly of the loss of so many artistic voices in the trenches, then it also points quite clearly to the intimacy of portrait sculpture. The act of producing a portrait, in 3D, under one's own fingers, is a hugely immediate process. "There's a very powerful connection," says Gibbon. "There is a tiny sculpture by Rodin, the head of Ugolino, in which expression is bursting out of the bronze form in a very emotional way. It really demonstrates Rodin's response to the human mind and body."

Amongst the many highlights of this extensive exhibition, ranging from antiquity to the modern day, there are 18th-century wax portraits of royalty, Renaissance portrait medals, a bust of an Ancient Greek councillor and a Maori carved wooden head which it is believed was cut from the central pole of a Maori meeting house.

"There are plinths of all different sizes displaying heads looking in all directions," says Gibbon. "Wherever you look, someone will be looking back at you."

Head To Head: Portrait Sculpture, Ancient To Modern is at Scottish National Portrait Gallery, 1 Queen Street, Edinburgh (www.nationalgalleries.org, 0131 624 6200) until January 10, open daily 10am-5pm (Thursday until 7pm)