SOMETIMES the most intelligent thing government can do is drag its feet. That's what Congress has, wisely, forced the Pentagon to do on the proposals for wider use of polygraph, or lie detector, testing which have been made by the Defense Department itself and by President Reagan. The problem with lie detectors is that they measure stress, not prevarication, and therefore are not very accurate indicators of whether a subject is telling the truth--as was pointed out by none other than the acting assistant secretary of defense for health affairs, Dr. John F. Beary. Forcing job applicants to take such tests and firing jobholders who don't could cause great injustice without making the government any the wiser about breaches of security.

Now both houses of Congress have voted to rescind any changes in the Pentagon's lie detector rules and to prohibit any changes through next April. That decision represents a sensible caution and skepticism about the claims of lie detector enthusiasts. "If Congress has these concerns, we're willing to go up there to make our case," says L. Britt Snider, Defense's director of counterintelligence and security policy. That is a constructive attitude, recognizing Congress' authority and acknowledging by implication that the problem is not so urgent as to require an immediate drastic solution. By all means, let lie detector backers try to make their case. But we have a feeling that when they do, Congress will be pleased that it stopped precipitate action this time and will be persuaded that a little more constructive foot-dragging on this issue will be in order.