It might be easier to do something about North Korea’s nuclear truculence if we could make head or tail of the cryptic videos it has been posting on the web. The latest shows a dreaming man, some Korean script and a video of rockets flying through space while fires burn in skyscrapers and a pianist plays “We Are the World” at dirge tempo. Is this a harmless fantasy? A thrown-down gauntlet? Should the west respond with a statement? Should it post a video of its own? It is hard to know. Our traditional media are being “replaced” by the internet. But the “information” coming out of the information economy is often hard to decipher, and composed for purposes that are hard to discern.

The film academic Stephen Apkon argues in The Age of the Image , published this week, that it is possible to speak of a new kind of literacy, one built on figuring out such non-verbal messages. At its humblest level, his book is about the “language” of film, but Mr Apkon has a larger philosophical point, too. Our culture is growing more global. While it still relies on words, they are increasingly wrapped up with images, and it is the images people remember. Elizabeth Daley, dean of the University of Southern California’s School of Cinematic Arts, believes writing today is like Latin on the eve of the Renaissance – the language of a scholarly establishment. YouTube clips and other visuals are the equivalent of vernacular Italian. They are the street language, and the medium for much new and creative thinking.

Images have always mattered in public arguments more than we admit. Few people cared that Richard Nixon won the 1960 presidential debates against John Kennedy, so unkempt did the Republican look. Mr Apkon quotes a neuroscientist who says people are so attuned to picking up subtle signals that they make decisions about whether they like or dislike politicians “immediately”. And unsubtle, non-verbal messages with a great emotional wallop can now be broadcast more widely. Video of the shooting of Neda Agha-Soltan, captured during June 2009 protests against irregular Iranian elections, spread round the world. In the gut-wrenching Kony 2012 video (100m views in six days), American activists sought to enlist the US military in a manhunt for a Ugandan warlord.