Sometimes the House of Lords throws out speeches so interesting and radical, that you simply cannot imagine them being made in the Commons. One such came this week from the neuro-biologist Susan Greenfield. She asked a question that affects all of us, yet which I have never heard discussed by mainstream politicians: is technology changing our brains?

The context is the clicking, bleeping, flashing world of screens. There has been a change in our environment that is so all-embracing and in a way so banal that we barely notice it. In just a couple of decades, we have slipped away from a culture based essentially on words to one based essentially on images, or pictures. This is probably one of the great shifts in the story of modern humans but we take it almost for granted.

It is most striking when you watch children and young adults. This is not just the obvious ageing person's whinge because my kids can sort out computer or digital camera problems that baffle me. It is more about the way they absorb information and entertainment.

There are the "icons" (a word to dwell on) of the iPod or Windows, those cute and reassuring little pictures that perform the role of Chinese ideograms rather than western culture's words. Then there are the winking corporate mini-logos, which are more familiar to children than national flags or famous authors. Just watch a teenager navigate, with thumbs or fingertips, a world of instructions, suggestions, offers and threats, scrolling through songs, adverts, film clips and software.

This, of course, is only the start of the new world. What is actually on these enticing little cubes of plastic? My children communicate by text and computer messaging, using the concertinaed, post-grammar, post-spelling shorthand that everyone under 30 finds normal and everyone over 40 finds menacing. There can be little doubt that the structures, never mind the surface form, of the English language are changing fast.

But the main change is that even these shorthand sentences are surrounded by pictures. With mobile phone cameras, digital sticks and emailing, people no longer need to describe where they are but can just point, click and show a view, a friend's face or "happy slapping". Children carry portfolios of images on their mobiles and send each other more. The latest iPods and similar gadgets are used as much for watching TV shows, film clips or music videos as for listening.

Most people are probably ambivalent about all this. We know the world is changing and don't want to seem fuddy-duddy or to be left behind. We are instinctively nervous about the new culture of icons and pictures but shrink from saying it is worse than the old culture of long bored afternoons, with the rain drumming on the windows, struggling to concentrate on a book. Pictures are easier on the eye; why hesitate?

The brilliance of Baroness Greenfield's speech is that she wades straight into the dangers posed by this culture. A recent survey of eight-to 18-year-olds, she says, suggests they are spending 6.5 hours a day using electronic media, and multi-tasking (using different devices in parallel) is rocketing. Could this be having an impact on thinking and learning?

She begins by analysing the process of traditional book-reading, which involves following an author through a series of interconnected steps in a logical fashion. We read other narratives and compare them, and so "build up a conceptual framework that enables us to evaluate further journeys... One might argue that this is the basis of education ... It is the building up of a personalised conceptual framework, where we can relate incoming information to what we know already. We can place an isolated fact in a context that gives it significance." Traditional education, she says, enables us to "turn information into knowledge."

Put like that, it is obvious where her worries lie. The flickering up and flashing away again of multimedia images do not allow those connections, and therefore the context, to build up. Instant yuk or wow factors take over. Memory, once built up in a verbal and reading culture, matters less when everything can be summoned at the touch of a button (or, soon, with voice recognition, by merely speaking). In a short attention-span world, fed with pictures, the habit of contemplation and the patient acquisition of knowledge are in retreat.

Is this, perhaps, the source of the hyperactivity and attention deficit malaise now being treated with industrial quantities of Ritalin, Prozac and other drugs to help sustain attention in the classroom? If so, what will these drugs do in turn to the brain? Greenfield points out, in some of the most chilling words heard in the Lords, that "the human brain is exquisitely sensitive to any and every event: we cannot complacently take it as an article of faith that it will remain inviolate, and that consequently human nature and ways of learning and thinking will remain consistent".

While not suggesting a revolt by mere democracies against the corporate power of the IT industries, Greenfield suggests this is an idea that should at least be investigated further. She wants more government funding for the scientists and educators trying to understand the impact of the digital-picture world on how children learn to think - surely a more important area for state-backed research than endless lifestyle or obesity surveys.

Politicians should be seriously concerned. Parliamentary democracy has depended on a citizenry prepared to think logically about policies, to remember promises and to follow arguments. Greenfield's feared world without context is therefore also a world more prone to political illogic and fad. At the memorial service last week for Lord Merlyn-Rees - a politician of integrity and decency - I was surrounded by many great political figures of the 70s and 80s. But I wondered how many of their patiently made arguments would be given house room in the exciting digital wasteland.

Perhaps not surprisingly, we are not getting a worried or intelligent response from today's politicians to this great shift in how we learn and think. They prefer to boast about the tunes they download on to their iPods, or court publicity for their website inanities. But they could all take a valuable 10 minutes to read and reflect on Baroness Greenfield's fine speech. It's available in a hard copy of Hansard, or at internet. Yes, really.

jackie.ashley@theguardian.com

Note: Merlyn Rees, when ennobled, became Lord Merlyn-Rees, with a hyphen (in fact, Lord Merlyn Merlyn-Rees)