"I looked into Mr. Putin's eyes," U.S. Sen. John McCain, an Arizona Republican, joked after meeting Russian President Vladimir Putin, "and I saw three things: a 'K' and a 'G' and a 'B.' "

McCain was referring to Putin's earlier career as a skilled operative in the Soviet Union's intelligence services, stationed in Dresden, East Germany. Despite McCain's quip, however, Putin seems to lack a key spy asset: an opaque poker face.

Others have attempted to read Putin's ever so expressive visage. U.S. President George W. Bush's first face-to-face meeting with Putin in 2001 was one much-cited example. After looking into the Russian leader's eyes, Bush declared, he now had "a sense of his [Putin's] soul." After the meeting, Bush said he had found the Russian leader to be "very straightforward and trustworthy."