The anonymous telephone call is the most common sex offence of all. At least 10 per cent of women with a private telephone receive obscene calls every year. But the call made for sexual excitement is surely different to the hoax call, which has so dogged the police during their search for baby Abbie Humphries - or is it?

One common theme is the thrill of power, perhaps unattainable by any other means - the 'Gary' hoax call led to a special televised appeal directly made to him.

This appears all too similar to the temporary power gained by the obscene caller. In one reported case, the offender said: 'It is wonderful how with one word a man can embarrass a woman. First they blush with shame, then they become furious. It seems to me I am a magician with unlimited power.'

But the hoax caller is usually younger than the obscene caller, and in contrast sees the call as an extreme practical joke. Since pranksters love cocking a snook at authority, what better than to make the police look fools? Especially if you have been in trouble with them.

But why should the Abbie Humphries case attract so many hoax calls? It appears that many could be viewed as a form of voluntary confession by the innocent. Crimes given wide media coverage often attract such false confessions, and kidnapping appears to particularly draw the confessor.

Perhaps a clue to motivation comes from the fact that kidnappings often extend over a long time, and therefore receive extensive media attention. So the most important reason for the hoax confession is a pathological desire for notoriety.

Gisli Gudjonsson, an eminent forensic psychologist, reports a case of a man who voluntarily but falsely confessed to eight murders between 1979 and 1986. The man admitted to Gudjonsson that he found confessing to gruesome murders 'very exciting'. He also described feeling consequential when the murder investigation began to involve him. It appears to have increased his self-esteem.

Psychologists speculate that some people have high levels of generalised guilt. They feel some responsibility even for events that have little to do with them.

Televised appeals may contribute to this drive in the generally guilty to confess; the appeals emphasise all the positive aspects of confession to suspects, and display immense approval for such actions. Given that confession usually produces some relief from anxiety, in the absence of a relationship with a more accessible authority figure to confess to, this may explain why some falsely come clean to the police.

However, the national impact of a crime may attract false confessions for a different reason. Those suffering from serious psychiatric disorders where the ability to distinguish reality and fantasy has broken down may feel appeals are being addressed to them personally, or may confuse their own wish for a child with the idea that they took the child themselves.

This kind of caller is usually quickly detected, but the situation is more complicated with the inadequate and lonely who are so unused to anyone taking what they say seriously that the only way they can receive attention is to phone the police and claim some knowledge of a notorious crime.

The telephone has the particular advantage for the immature personality that there is no physical confrontation, so the caller can construct a huge fantasy which is difficult for the listener to challenge. Since anonymity is essential to all these behaviours, it may be the only form of communication possible for anyone incapable of straightforward social intercourse.

So behind the perfectly anonymous technique of the hoax caller lies a paradoxical desire for self-disclosure. This adds an ironic twist to the current British Telecom advertising campaign - 'it's good to talk . . .'. Perhaps, but is it always good to


Dr Raj Persaud is clinical lecturer at the Maudsley Hospital, London.