Each year, at the end of October, groups of small shadowy figures can be seen wandering around the streets of Britain, moving from house to house, offering an eerie threat to householders who have no idea of who is challenging them, or of what the consequences of their refusal may be. Occasionally a face may be recognised, but more likely the challenge "trick or treat" will be issued by some ghoulish, luminous Dracula or Frankenstein.
To many, the increasingly popular phenomenon of "trick or treat" at Hallowe'en is another sign of American cultural imperialism, a ploy to prise goodies from an unsuspecting public and, to some, a dangerous time of year. To scores of children, however, the chance to put on a mask and make chilling demands is thrilling. The anonymity and the cunning trickery of the mask can be exhilarating.
But the simplicity of the Hallowe'en mask disguises a long history. Dracula is at the banal end of an art-form that in many parts of the world is the equivalent of opera in dramatic presentation, musical accompaniment and passion.
The thing people put over their faces is just one part of the spectacular art form of masquerade - a word that means both the complete costume of the mask-wearer, and the event at which the mask is worn. In Europe, the mask has been reduced to an entertainment, a disguise, and we have forgotten the power that masquerades have to inspire both awe and terror.
Nobody knows when masks were first used, but the figure of the half-man, half-stag painted in the caves of Altamira in Spain (and thought to date from the early stone age) indicates that they have long been a part of human culture. The word "masquerade" probably derives from an Arabic word, "mashkara", which is also the root word for mascara. The verb from which this word derives is "Skhr", which means to laugh, to scoff or to ridicule, something that all masquerades do.
The origin of what Western peoples think of as the mask derives from the Greeks' role-playing theatrical mask. This was renamed in Rome as Persona. Only privileged Roman families were allowed to own ancestral masks - if you owned one it meant you were a freeman with an established family bloodline, not a repressed slave.
In other cultures, the mask hides a real change in the performer. Many African masking traditions emphasise that a performer's real identity has been changed for another. This might be the identity of a spirit, thought to have come in from outside the community, often from the surrounding bush or rainforest. The images (iconography) of these `masks often reflect this. Wild animals, such as the buffalo or leopard, or a combination of different elements from the forest, such as birds' feathers, palm leaves and tree fibres or animal hides (probably the origin of the legend of the Green Knight or Green man in European folklore) often feature in the masks.
Alternatively, the spirit may be believed to be that of an ancestor returning to earth from heaven, either to bring blessings or to extract homage. The masks that come out for Hallowe'en (the night of All Souls) are not, after all, so far removed from the ancestral masks of Africa.
The transformation of a person into a spirit often meant masquerades were used to transform people from one status in life to another. This was particularly true in Africa, where the transformation of children into adults often involved masqueraders arriving at a village and "kidnapping" children to be initiated into adulthood. Children would be taken into the forest in a disorientated state, where they would be educated in the skills of adult life. Finally, before the new adults were taken home, the masqueraders would take their masks off, showing that there was really little to fear.
In the modern world, masks are used for different purposes. We are very used to seeing masks as protection (such as the welder's mask) or as a means of concealment (the terrorist's balaclava or the rock star's sunglasses). But masks are most often associated with performance. In many instances a mask enhances the dramatic effect or emphasises the character of the role being portrayed. It is this aspect that predominates in the European tradition.
Some of the African traditions continue to this day, but increasingly masquerades are seen as entertainment. It is this aspect of masking that has the widest recognition around the world, particularly in the form of carnival. Carnivals, with their colourful floats, are the greatest expression of the masquerade. They developed in the creative clash of European and African cultures in the Caribbean carnival, which usually takes place in the week before the beginning of Lent, was a part of the European Christian culture (Pancake day) and involved masks. When slaves brought from Africa were forced to adapt their African traditions to Christian festivals, carnival provided the perfect setting. Nowadays, the spread of African culture has meant that the vibrancy of masking can be enjoyed throughout the world.
Both carnival and Hallowe'en are good times to introduce masks to children. Anything can be used to make a basic mask, providing it covers the face.
The diversity of mask styles means that the sky's the limit in terms of creative imagination. But a number of themes are common to masks from different cultures. The human face is one, often distorted into caricature or a dramatic personality. Another is that of the wild, represented as untamed animals. The point is to make a difference in character, so that anybody putting on a mask will change their personality to suit that of the mask.
If the mask is made in secret, guessing the name of the wearer underneath it is often a revealing exercise.
Dr Will Rea is a lecturer in anthropology at Goldsmiths College, University of London Photographs by permission and with the assistance of the Horniman Museum, 100 London Road, Forest Hill, SE23 3PQ.
For details of the museum's education programme, exhibitions, or to view the mask collection, call 0181-699 1872 (ext. 157)