It took a while, but investors eventually decided they liked what they heard from Ben Bernanke, and stock indexes rose enough on Friday to put them into positive territory for August.

Stocks gyrated after the Federal Reserve chairman spoke on Friday morning. They first gave up their morning gains, then bolted to their highs for the day, before settled in-between.

The Dow Jones industrial average ended the day up 90.13 points at 13,090.84.

Investors have been watching to see whether the Fed will buy more bonds to further lower long-term interest rates. Stocks fell initially, however, after it became clear that no such announcement was coming Friday and that Bernanke had stopped short of committing the Fed to any specific move.

Still, he said the Fed “should not rule out” new policies to improve the job market.

Stocks rebounded once investors parsed his comments. At one point the Dow was up as many as 151 points.

The Standard & Poor’s 500 index closed up by 7.10 points at 1,406.58. The Nasdaq rose 18.25 points to close at 3,066.96.

The Dow finished the month of August up by 0.8 percent. The S&P 500 rose more than 2 percent for the month, and the Nasdaq rose more than 4 percent.