Idealists have been scoring a few points lately in the highly pragmatic game of mutual fund investing as modest principals generate sizable interest payments.

Consider the 1990 results achieved by three prominent "social responsibility" funds with portfolios selected according to social or ethical standards:The Pax World Fund was up 11 percent; the Dreyfus Third Century Fund 4 percent, and the Calvert Social Managed Growth Fund 2 percent, according to calculations published by the Mutual Fund Forecaster, a Fort Lauderdale, Fla., investment advisory letter.

Those gains were achieved while just about all the stock-market indexes were posting losses for the year.

That may come as heartening news to the many fund investors who aim to promote ethical and moral, as well as dollars-and-cents, values as they choose where to put their savings to work.

But some financial advisers remain skeptical about the long-term effectiveness and workability of social-conscience investing.

Over sustained periods, they say, the performance records of ethical and social-value funds remain subpar. Furthermore, these analysts argue that the whole idea behind the funds seems flawed.

"The fundamental problem with social-responsibility investing is that a single nonfinancial criterion effectively eliminates a huge number of stocks from further portfolio consideration," says Norman Fosback, editor of the Mutual Fund Forecaster.

"Any time you restrict an investment universe, especially in a drastic fashion, you reduce the range of potential profit opportunities."

From the end of 1981 through the end of 1990, the three funds Fosback follows posted total returns ranging from 151 percent to 240 percent, while Standard & Poor's 500-stock composite index was registering a 289 percent return.