One of the more difficult tasks parents regularly face is breaking the news to our moppets that the incredible story they have just told us is an urban myth.
Recently I heard for the first time the one about the pet python. After a lifetime spent sleeping coiled up on its owner's bed, one night it stretched itself out to its full length. On describing this to a vet, the owner was told the python was measuring her up to see if it could swallow her. The telling of this anecdote was prefaced with "I know it sounds like an urban myth but it's not." A quick check of snopes.com revealed it was.
However, children soon get over their disappointment and, with encouragement, develop critical thinking abilities. Those who don't can be found on both sides of the microphone on talkback radio.
A few days ago, I heard a talkback host say he had been told that 50 per cent of new HIV cases in Greece were self-inflicted to gain that country's very generous benefit for those with the condition.
It had a lot of the hallmarks of an urban myth (which it was); an element of the macabre; a source called "someone told me"; emotional triggers. And everything about the snippet also made it perfect for talkback radio.
It alluded to Aids, which is still a sure-fire attention-getter among the always-ready-to-react crowd.
It worked only because it was short on specifics. Without knowing how many new cases of HIV were recorded in Greece, it was impossible to assess the significance of this factoid. If there were only four new cases, for instance, then this phenomenon could be confined to two people, each of whom talked the other into it.
It relies on hearsay. "I've been told". By whom? A leading European epidemiologist or a slobbering madman on a street corner? Unless you have authority for statements like this, they are worthless.
It apportions blame for a complex event in an oversimplified manner: the global economy, you are welcome to infer, nearly collapsed because some lunatics took Greece to the brink of disaster with their sick plan to rort the welfare system.
Without stating so directly, it pictures beneficiaries as parasites who will do anything, no matter how outrageous, to leech from the state.
No one is forced to listen to such drivel, of course. But many people do. Surely there's enough unavoidable stupidity in the world without exposing ourselves to more of it voluntarily?
At first glance the case of Ioana Teitiota, the Kiribati citizen who claimed refugee status here because global warming threatens the survival of his homeland, looked to fall somewhere between trying it on and having a laugh.
Leaving aside the niceties of argument over what exactly constitutes a threat to someone's human rights - the basis of this claim - we must acknowledge that as rising sea levels inevitably threaten populations around the world we can expect a growing wave of environmental refugees.
We don't have to look far to find a precedent. When a combination of drought and dust storms made their homes unliveable in the 1930s, the residents of the United States dust-bowl states migrated en masse. A total of 2.5 million people left their homes to seek refuge elsewhere.
They, too, were unwelcome but they persisted because they had to. That catastrophe was also the result of humans ignoring the effect they were having on the environment, in this case by over-cultivating the land.
The Teitiota case has been reported around the world, presumably because it is seen, rightly, as an early sign of an apocalyptic scenario to come.