They find that central bank "talk" acts somewhat as a counterbalance to prevailing market conditions. This effect is most pronounces where we think it would be: cash constrained, cyclical firms.
From the abstract:
"...central banks influence financial markets' expectations of its future policy. In bad times, monetary policy communication inducing an upward revision of the path of future policy is good news for stocks. During an expansion the effect is weak and on average negative...."and from the paper itself:
"We show that there is a role for central bank communication. In contrast to earlier studies we find that central bank communication has an impact on stocks. The impact is expected to be the most pronounced for financially constrained companies in cyclical industries during a recession"Incidentally, this is also my new winner of the best title for a paper, EVER. Can the Fed Talk the Hind Legs Off the Stock Market? (June 13, 2011). Paris December 2011 Finance Meeting EUROFIDAI - AFFI. Available at SSRN: http://ssrn.com/abstract=1943558