What central banks may have the world over is a failure to communicate.

Officials are struggling to spell out their visions for monetary policy, often amid a chorus of competing views. Chairman Ben S. Bernanke is trying to manage expectations about when the U.S. Federal Reserve will slow asset purchases and raise interest rates. Bank of Japan Governor Haruhiko Kuroda's reflation-push is backfiring by driving up bond yields. European Central Bank President Mario Draghi is dashing investors' hopes he once kindled for extra stimulus.

The muddied messaging already is roiling financial markets, threatening to undermine the confidence of investors, households, and consumers and so undoing efforts by central banks to strengthen their economies. The opacity puts policy makers under pressure to improve the communication techniques they've been using to restrain borrowing costs.