Commentators, noting the similarities between the economic policies of Britain's Margaret Thatcher and America's Ronald Reagan, have been looking to England for clues as to how Reaganomics might work.

Their emphasis has been on jobless rates, deflation and revenue generation -- the things economists are most comfortable talking about.

They'd better start looking as well at the social fallout. It isn't fair to suggest that the recent riots in England, unprecedented in scale and duration, stem solely from Britain's stringent economic policies, or that riots will occur here when Reagan's very similar policies start to take effect. But you have to be blind -- or an economist -- not to see the connection.

The point is not that the theories are wrong, though I suspect they may be. But even if they are right in principle, even if the tax cuts and tight money and a reduction in social programs are necessary to spark a resurgence in private business activity and bring inflation under control, the unrest in Great Britain is a warning that people won't starve quietly while they wait for theories to take hold.

Thatcher has been sticking by her guns, in the face of a slumping economy and the worst unemployment rates in years, because, according to her theory, it will take time and a good deal of economic discomfort, before her policies succeed. In the long run, she is convinced, everybody will be much better off.

Reagan and his principal advisers have been offering the same counsel: it may take a couple of years, and some individual suffering, but the long-term results of Reaganomics will make it all worthwhile.

The problem with the theories, here and in England, is that they are based on economic models that take too little account of the fact that people behave not just as economic units but as social and political creatures as well. The models allow economists to tinker with various appraoches: tighten this, loosen that and leave the other thing alone.

Quite often, the models predict actual behavior fairly accurately: reduce taxes, and you increase the amount of money people spend on non-essentials; raise the taxes on savings interest, and you reduce the amount of savings -- just as the model predicted.

What the economists too often overlook is the fact that economic behavior is just one kind of behavior. There are other kinds, including what has been going on in England the past couple of weeks, but many economists see the other kind as "political" or "social" and, therefore, outside their area of expertise.

Well, economic models are no better than the factors that go into their construction, and guesses about political and social reactions are just as important as predictions regarding market decisions.

I know economists who can demonstrate convincingly that rent control diminishes supply of housing, while free-market economics increases it. Thus, they argue, everybody -- including the low-income families whom rent control is supposed to serve -- would be better off it we simply repealed rent control.

The theory is right is you only consider market behavior over a substantial period of time. In the short term, though, repeal of rent control means that a lot of people will be forced out of the housing they now occupy, and since they will not be inclined to wait a dozen years for the marketplace to work its magic, they may take to the streets instead. Any model that doesn't allow for that possibility isn't worth feeding into the computer.

The Reagan administration may be properly convinced that its policies will work over the long haul to increase the supply of jobs and diminish the necessity for welfare, food stamps, job programs and other benefits. The people who lose those benefits, however, are not likely to wait quietly for the long haul. What seems far more likely is what is happening in the Streets of England.

True, there are other factors that account for the British riots: racial animosities and heavy-handed police tactics among them. But if these other factors have provided the tinder, it seems reasonably clear that joblessness and the sense of hopelessness that are the immediate results of the Thatcher economic program have supplied the match.

It would be foolish to make the outright prediction that there will be riots in the streets of America when the Reagan cuts in social programs finally hit home in the coming months. But it would be more foolish still for the administration to ignore the possibility.

The British unrest has to be considered fair warning.