We don’t need research scientists with monitoring devices to tell us stories have powerful physiological effects - fascinated though I would be to see a precise read-out of heart rate, muscle tension, pupil dilation, rise in skin temperature and so on among a class being read one of my books.

We report our experience of story in physical terms. “It made my hair stand on end.” “It made me laugh so hard my jaw hurt.” “Stomach-churning.” “It gave me the shivers.” Or, as my seven-year-old son said of one gruesome tale: “That story makes my mouth go sideways.”

If we acknowledge stories can have such radical effects on our bodies, we should also acknowledge our profound psychological and subsconscious reactions.

(At this point a Cree or Navajo, whose people use stories in their healing ceremonies, would be waiting for me to stop stating the obvious. Jung, too, documented the use of stories in the treatment of neurosis.) Reading a shoddily written book to the end, feeling our attention held by a badly-acted film or blinking back to the real world after being glued to an episode of some imported soap is further proof that there is something under the surface of a story that magnetises our nervous systems. I have been exploring these “depth-charges” with teachers and students over the past four years and have come to think of them as “deep story structures”.

These structures appear few and simple, despite the astonishing variety of the stories they underpin - but then life itself is based on the beautiful, simple double helix of DNA. I am not talking about plots, but about that something as fundamental as DNA, which separates a living story from the inert matter of rambling discourse.

I believe the entire canon of the world’s stories may be based on three or four such structures. Exploring them in the classroom, I have seen students’ attitudes to the writing of creative prose transformed.

Given three simple diagrams (see below), year 9 pupils soon grasp what Beowulf, the film Jaws and the reports of the tragic events in Dunblane have in common. Writing prose is no longer a high-wire act of stringing words together over an abyss, but becomes a question of working with patterns which have profound relevance to their own human experience.

THE RELATIONSHIP

This structure represents the pattern by which the life paths of two strangers meet - the moment of encounter that will decide whether or not further meetings take place. Most stories depth-charged by this pattern start at that decisive moment, where two paths meet. Romeo sees Juliet, Lady Chatterley encounters Mellors. We follow the process of encounters down the stem of the Y, wondering about and anticipating the outcome of this love affair or friendship.

Without the meeting and mating of strangers none of us would exist. No wonder we find this structure exciting. Exploring it with adolescents, at the time when their ideas about how relationships proceed are in flux, can be enormously rewarding. Ask simple questions to start them off. Who are your two characters? Where will they meet? What happens that makes them want to meet again?

THE INVITEDUNINVITED GUEST

The successful outcome of the relationship structure is conception - a baby is either an invited or an uninvited guest - but as Samuel Beckett says: “We give birth astride the grave.” The arrival of death (another guest) is a foregone conclusion.

Stories depth-charged by this structure explore how a pre-existing circle of people is affected by the arrival of a stranger. Will the stranger be benign or a threat, assimilated or ejected? In Beowulf the stranger is a Grendel. In a coastal resort it is a great white shark. We all know the terrible consequences of the stranger’s arrival in Dunblane. In my own novel, The Nature of the Beast, unemployment, a metaphorical beast, is the uninvited guest in a community.

Hollywood director Stephen Spielberg used this structure in his films ET, Jaws and Gremlins. It is the basis of most genre writing - horror, ghost stories, crime, westerns and much science fiction. As a culture we are obsessed with this pattern. Most news bulletins are constructed around it, with a hurricane, Aids or cancer as the uninvited guest.

This particular “depth-charge” has such power because it deals with our greatest mysteries and fears. As babies entering the circle of our families, were we invited or uninvited guests? We have all been the stranger and part of the circle.

Perhaps our culture’s apparent obsession with the inviteduninvited guest pattern reflects a temporary erosion of vision and spiritual purpose. Perhaps we should not be too surprised that our boys, if they read at all, read horror - stories depth-charged by our concerns about sex and death - at a time when male purposes and goals have never been more in question.

Again, the starting points are simple. Who is in the circle? A family? A gang? Who or what is the stranger? Cancer? The death of a grandparent? A dog in the playground? Will the stranger be ejected or assimilated?

THE QUEST

A quest is a journey with a purpose. We set ourselves goals as we attempt to make sense of our lives. Some of these are conscious (“I want three A-levels”). More powerful, perhaps, are the subconscious ones (“I want my father to love me”).

The diagram shows the ditches and hurdles that make stories about quests interesting - the obstacles that must be overcome by Sir Galahad and Indiana Jones. A quest need not be spiritual for it to be profound. My husband, adopted at birth, searched for and found his blood mother. Some quests are silly but satisfying - Jane Hissey sends Little Bear to find his red trousers.

What kind of person is your main character? What is the goal? What obstacles must be overcome?

Obviously, the more complex a narrative, the greater the likelihood that more than one depth-charge will be operating - just as in real life an encounter with a stranger or the death of a parent may wake us to new goals. Sir Gawain and the Green Knight begins with a classic uninvited-guest pattern but becomes a quest.

My own quest to pin down a fourth structure continues, taking in the “trickster” cycles of stories which proliferate in cultures where the idea of dream quest or vision quest is strong: the native Americans’ Coyote and Raven, for instance, or Mulla Nasrudin in the Middle East, the Idle Jacks and Lazy Sons of Traveller tales, Anansi in the African tradition. Tricksters provide startling, amusing jump-starts to the imagination and help to overcome difficulties and obstacles.

These ideas should not be explored glibly. Anything that can raise the hairs on your arms or quicken the beat of your heart is a powerful force. But allowing students to apply their considerable experience of stories from all media to these patterns opens up fresh and fascinating dialogues. The more highly-equipped the young person is with the tools of writing - simile, metaphor, descriptive writing, characterisation - the more interesting the results.

We are pattern-making creatures. The search for structure in an unfamiliar text such as Beowulf can be hot and excited after a discussion of Jaws.

The sense of well-being, the renewal of enthusiasm which comes after storytelling can warm a classroom like a newly-lit log-fire.

Janni Howker’s collection of short stories, Badger on the Barge, and novels, The Nature of the Beast and Isaac Campion, are published by Walker. Her shorter novel, Martin Farrell, is published by Red Fox