Some things are so obvious that whether they are true or not seems almost beside the point.

Take the link between unemployment and crime. Even if a number of researchers hadn't documented the fact that crime rates and jobless rates often rise and fall in tandem, you would know instinctively that the two had to be linked.

And you would go right on knowing it after a careful study demonstrated that it wasn't so -- at least not to the extend commonly believed.

For a couple of years now, New York's Vera Institute has been trying to determine just how real the link is. The study still has a couple of years to go, but preliminary results cast doubt on the notion that the jobless are drawn into criminal activity because of their joblessness.

For instance, in one of its pilot studies, Vera interviewed some 60 inmates of Rikers Island just before and again just after their release, trying to learn why they chose to commit crimes.

According to project director James Thompson, only three or four of the inmates said they committed crimes because they had lost or could not find jobs. Several said they engaged in criminal activity to supplement their legitimate income; some said they had given up on work because the benefits of crime were more attractive; many said they either worked or stole to support themselves, though not at the same time.

One young man was quoted as saying: "If you're working and you see something you want, you wonder how you're going to pay for it. If you're not working and you see something you want, you wonder how you're going to take it."

Said another: "If the job pays good, I'll go to the job. It the street is good, I'll go to the street."

I asked Thompson whether it might not be a mistake to base broad conclusions on what young offenders, many of whom understand their own motivations only dimly, had to say about why they did what they did.

It was my notion that the general state of employment in a given area might have had as much influence on criminal activity as the employment status of a particular person. That is, in a slow economy, isn't it possible that a youngster will look at his "square" older brother or uncle who has been laid off and decide that being straight doesn't really pay off?

Thompson agreed, but only up to a point. He reminded me that figures on "adult" crime frequently include offenders who are still children. For instance, fully a quarter of those arrested for crime in New York City are 16 or 17 years old, though they are called adults. The median age is something like 19.

It's clear, he said, that employment cycles have very little to do with a 16-year-old's decision to lift a wallet or to bash an old lady over the head for her pocketbook.

Moreover, he said, the highest-risk crime group comprises lower-class minority males between the ages of 16 and 20, most of whom are completely outside the work economy and, therefore, not affected by overall fluctuations in employment rates.

Thompson suggested that the general state of the economy may influence crime rates in unsuspected, quite indirect, ways.

Businesses that flee to the suburbs because of high inner-city crime rates take their jobs with them. Thus the absence of job opportunity is "linked" with an increase in crime. But it doesn't necessarily follow that the former causes the latter.

Others have suggested that judges may become harsher and more inclined to hand out jail terms (which can show up as increased criminal activity) during periods of economic difficulty because the judges themselves feel more threatened by crime during such periods.

One researcher suspects that unemployment "causes" crime in yet another way: "The cop whose wife is laid off her job during an economic downturn might decide he has to supplement the family income. One way to do it is to make additional arrests in order to earn the overtime that goes with court appearances.

"A lot of these arrests might be for offenses that he would have ignored at another time. But the statistics will reflect an increase in the crime rate."

Vera's Thompson said their pilot studies turned up a phenomenon he described as "maturing out" of crime. For young teen-agers in the high-risk group, crime offers "more visible and more desirable sources of income." Later, they may alternate between criminal activity and "straight" work, working when the risk of getting caught seems high, or doing crime when working pays too little. Still later, the pressures of adulthood and family ties may render criminal activity increasingly unattractive.

The Vera study is still far from complete, but already the results suggest that much of what we "know" isn't necessarily true.