Brainbox, by Xbox

Before pubs were transmogrified into svelte wine bars, their walls often displayed gimcrack homilies, a favourite being "Everything I like is either illegal, immoral or fattening". Coming fresh to a book called Everything Bad Is Good for You , one might have expected it to be about things illegal, immoral or fattening. Instead it is about video games, television and the internet - the bogeymen for many parents and social commentators. But bogeymen come and go. In their early days, novels were widely viewed with much the same alarm as TV and PlayStations today.

The old pub maxim is a sly comment on the puritanism endemic in our culture: too much pleasure is bad for you. As his book title suggests, US writer Steven Johnson could hardly disagree more. Video games grow ever more complex; TV drama, comedy and even game shows are increasingly intricate; and the internet is intellectually demanding and challenging. In each case, Johnson is less interested in content than in process: how are these media used? While the content of video games and TV programmes may or may not be trivial, the mental involvement of gamers and viewers is considerable. But then the content of chess - figures jumping about on squares in contrived ways - could easily be thought to be trivial; players' mental involvement most certainly is not.

Johnson shows how video games have evolved from relatively simple beginnings to their present-day complexity. Playing today's video games is not simply dependent, as is often suggested, on hand-eye co-ordination.

Deftness is necessary, but it is not sufficient. Snap decisions must be integrated with strategic objectives, and gamers learn if moves lead to disaster or success only by responding to situations as they arise.

At the same time, television drama plots have become "multi-threaded", with as many as seven or eight narratives in progress simultaneously in any one programme. Likewise, comedies have grown ever richer in innuendo - and not the sledgehammer innuendo of Benny Hill, but the wry innuendo of Friends , Seinfeld or, to cite a British example, The Office .

Even game shows and reality television, Johnson convincingly argues, nowadays demand, and get, much more viewer concentration and involvement than their equivalents of yesteryear.

None of this suggests a growth of popular mental lethargy. On the contrary, it shows the populace to be increasingly sophisticated in its cultural activities. For Johnson, this is confirmed by the fact that when carefully investigated, IQ tests show people, on average, to be getting cleverer and cleverer. Counter-intuitively, research also shows that keen video-game players are more sociable, more confident and more creative problem solvers than non-players. Moreover, non-players' abilities in these areas swiftly develop if they become keen players. Johnson explores whether these changes are due to any other cause and concludes that they are not. Therefore, he claims, the changes must be due to games and the media. ( Times Higher readers may be dismayed to learn that he does not believe that these improvements are the result of better education.) It is not fundamental to his thesis, but Johnson's final explanation of why much of this is happening is the book's only serious lacuna. He tries to marry the increasing complexity of media content to the profit motive - an archetypical American attempt to make enlightened self-interest the progenitor of all things bright and beautiful. It is in the financial interest of media companies to produce programmes that can be watched repeatedly on DVD and cable channels, he argues, because the profits earned from reruns now exceed the profits earned from first runs. And to be repeatedly viewable, programmes need to be many-layered and difficult to take in at first showing.

This is twaddle. Programmes that fail on first showing are unlikely ever to achieve significant rerun income. The add-on profits depend on initial showings generating word-of-mouth recommendation. But none of this invalidates the book's principal argument.

Few books about popular culture could be described as page turners, but Everything Bad gripped me from start to finish. Johnson writes with precision and clarity, carefully avoiding hyperbole and overstatement. He accepts, for example, that television and video games are not acceptable substitutes for reading books, and shows why.

Conventional wisdom bewails the dumbing-down of popular media and insists that playing video games and watching TV make people stupid. Codswallop. We believe all this only because, as the pub sign implies, we cannot accept that hedonistic activities are good for us. Over the years, society has managed to convince itself that ball games - and a host of other time-wasting recreations - help us develop physical co-ordination, team spirit, good health and strategic skills. Johnson's book argues that days spent glued to screens of various kinds should not leave us racked with guilt.

Winston Fletcher is visiting professor in marketing, Westminster University, and chairman, Royal Institution. For many years he worked in advertising.