The debate has raged for years among economists and policy makers: Do cuts in capital gains taxes stimulate savings and investment or do they merely give breaks to wealthy taxpayers?

Late last year, Congress lowered the taxes that individuals must pay on profits they earn from investments they have owned for a year or more.

In cutting capital gains taxes (on investments such as stocks, bonds and real estate), Congress said it did so to encourage savings and investments that would, in turn, make it easier for companies to raise the capital they need to expand and modernize.

A new study, undertaken by Opinion Research Corp. for the Securities Industries Association, reports that a quarter of the 516 middle and upper level managers surveyed either made new investments or increased the size of existing ones "as a result of the reduction in the capital gains tax cut."

More importantly, perhaps, the survey showed that 15 percent of those surveyed executives increased their investment in corporate stock.

Because of the low price of corporate stocks in recent years, companies have found it too expensive to finance their capital needs by selling shares to the public.

Last year companies sold only $3 billion of new stock to the public, compared with $10.5 billion as recently as 1975, according to fresh data from Salomon Brothers, a large investment banking firm.

Instead of selling stock, companies are either going into debt, holding back more of their profits (and by paying out fewer dividends, discouraging investors from buying their stock) or deferring new capital outlays altogether. i

The new survey -- admittedly a limited one -- suggests that capital gains taxes do affect savings and investments decisions by individuals.

It should be noted, however, that corporate executives might be more prone to invest in corporate stock than other high income individuals who have less daily contact with businesses.

The higher the income level of the respondent, the more likely he or she was to increase his or her investments and buying common stock.

For example, among individuals making $30,000 a year or less, only 10 percent increased their investments and none of the increase was in common stock. Most put their money into real estate, while a few bought mutual funds (which invest in common stock) or futures.

But 36 percent of the managers earning $75,000 or more raised their investment level and 25 percent of executives earning that much boosted their holdings of common stock.

Opinion Research Corp. put the question directly to 516 members of its so-called Executive Caravan, drawn from the largest 800 companies in the country.

According to Jeffrey Schaelfer, research director of the Securities Industry Association, the question asked was: "As a result of the changes in the capital gains tax law, did you make new investments or increase existing investments during 1979?"

Presumably other executives increased their investments in 1979 but for reasons unrelated to the capital gains cuts as enacted last year by Congress.

According to the survey, 4 percent of the executives increased their stockholding by less than $5,000; 3 percent increased their equity investment by between $5,000 and $10,000; 4 percent raised their stock ownings by $10,000 to $25,000. Another 2 percent added between $25,000 and $50,000 to their equity portfolios and 1 percent bought between $50,000 and $100,000 of new stocks.

"Evidently, given the proper incentives, common stocks are very desirable to those with funds to invest," Schaefer said in an article to be published later this week.