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Anyone can call a stock cheap on a gut feeling. To screen for stocks that are cheap based on evidence, however, it's useful to compare their prices to some measure of underlying value that isn't altered by investor fervor. Common measures for the job include the money a company makes (earnings, sales, cash flow), the money it returns to investors (dividends) and the estimated price of stuff it owns (book value). Oddly enough, there's also an expense category that works surprisingly well: research and development spending.

Money spent on corporate overhead subtracts from investor returns, but R&D is different. Companies spend today to create products and processes that will earn top dollar tomorrow. Not all experiments produce riches, of course, but research-intensive companies learn to spend money on the surest things, so R&D turns out to be a pretty good predictor of earnings growth. A 2004 study published in the Journal of Finance found that between 1951 and 2001, companies that suddenly boosted their R&D spending experienced faster profit margin growth and better stock returns than those that didn't.

If R&D predicts earnings, and if a low price-to-earnings ratio can help find attractive shares, a low price-to-R&D ratio should work, too. A 2001 paper that examined the matter found that it does; stocks with low price/R&D ratios outperformed those with high ones by six percentage points a year during the study period.

The three companies below are research-intensive, spending at least 10% of sales in the lab. They've increased their R&D spending by at least 10% over the past year. They also have price/R&D ratios below 30, the median for U.S. companies that spent on research over the past year.

KLA-Tencor

P/R&D ratio: 20
R&D growth, past year: 13%

KLA-Tencor (KLAC) makes test equipment that helps chip makers reduce their flaws and improve their yields. The past year was a good one for spending on such equipment (KLA reports fiscal year-end results Thursday), but many analysts expect spending to decline over the coming year as economic growth slows. KLA's sales are expected to dip 2% over the coming year. Much of its business is tied to smart phones and tablet computers, however, and the long-term outlook for both is promising. KLA shares trade at just nine times earnings, a discount of around 40% to the broad stock market, suggesting pessimism on the stock is overdone.

Abbott Laboratories

P/R&D ratio: 20
R&D growth, past year: 36%

Drug sales for Abbott Labs (ABT) rose 12% last quarter. The knock on the company is that too much of its sales come from Humira, an arthritis drug subject to patent expiration in 2016. Last quarter Humira contributed $2 billion of the company's $4.16 billion in drug sales. However, the drug's sales jumped 25% during the quarter on overseas growth and use in alternative ailments for which it has won approval, like for Crohn's disease and psoriasis. Abbott's research spending suggests the company is busily preparing for any future decline in Humira sales, and the company has nutritional, diagnostics and equipment divisions, too. Shares sell for 12 times earnings and come with a 3.7% dividend yield.

Analog Devices

P/R&D ratio: 22
R&D growth, past year: 12%

Analog Devices (ADI) makes chips that serve as go-betweens for the real and digital worlds, sensing the temperature in cars, the voices and fingers hitting phones, the light entering cameras and so on. Over the long term, increasing data traffic bodes well for the company, as does the increased computer content in cars and world growth in manufacturing. Like KLA, Analog Devices is subject to cautious estimates for the coming year. Early forecasts call for its sales growth to slow from 12% for its year fiscal ending October to 5% the following year. But shares nonetheless seem reasonably priced. They sell for 13 times earnings and offer a 2.8% dividend yield.