The Tate gallery: it's such fun]

IN THE glass cases were several cardboard cut-outs of a fat old man with no clothes. Benjamin Day, aged seven, from St Mary's Church of England School in Islington, north London, was unimpressed. 'It's not clever,' he said. 'Anyone could copy those.' His friend darted round the back of the case, head bobbing up and down on a level with the cut- outs, chanting: 'But they're worth millions of pounds]'

Pablo Picasso, whose cardboard figures from Manet's Dejeuner sur L'herbe were the object of Master Day's critical eye, would certainly have been pleased by his words. In adulthood he grieved over the fact that, at Benjamin's age, he was already losing the simple directness that children show in their drawings. At 12, Picasso drew with none of the easy genius of childhood but, he said himself, with academic precision and exactitude. The child's eye was one Picasso had to learn again. At its perceptions, on view up and down the Tate's galleries, people were smiling, some of them laughing aloud.

In the first week alone, 24,605 people came to see Picasso's sculptures and paintings exhibited side by side. There is Marie-Therese's plump face, with prominent cheeks and nose. And there again is the artist's hapless mistress, her features caricatured into curves like a bunch of bananas. And in another painting, sure enough, her face metamorphosed into a bowl of fruit. The visitors smiled.

Then Head of a Woman (1931), the sculpture of Marie-Therese's face as a heap of phallic objects. This had a curious effect. The men who looked at it broke into swift, irrepressible grins. The women, almost without exception, stared at it po-faced.

Not far away Morgan Edwards, aged five, was crawling under Picasso's famous The Goat, partly modelled from a wicker basket and a pair of pottery jars, taking a technical interest in areas which also interested Picasso. 'That's its bottom]' he observed triumphantly, patting the part with a very proper irreverence.

Picasso said, when his sculpture The Man with a Sheep was installed in Vallauris village square, that it should be set up so that children could climb on it and dogs pee against it. No dogs were present in the Tate to carry out Picasso's wishes, but the children present were sufficiently engaged to have scrambled all over his works, had the grown-ups allowed.

'That's brilliant]' said Robert Smith, aged 10, from Westminster Cathedral School, spontaneously, when he found Picasso's sculpture Baboon and Young. 'Look at the way they make the mouth out of two cars] I fink - it might be an old BMW. No, it looks like a Morris Minor. I like the tail, the way it curls up.'

Not that the children alone were excited. Adults too were joining in the game, spotting the Blue Peter-type components from which Picasso had made his sculptures, the wit, and the observation, the forks for crane's feet, the tailor's dummy for a body. It is a contagious game. 'Is she made from the drains you have in baths?' said a man standing in front of the sculpture Woman With the Key. He himself was long and thin, in a grey pin-stripe suit: you could have cut him from a strip of corrugated iron.

The more one looked at Picasso's sculptures, the dizzier the world began to seem. An elegant woman went past, pregnant, in clinging black, with a bow in her hair. Or was she a cooking pot and a pair of fans? A sculptor called Garfield from north-west London, in a black beret and a pair of dark glasses, had been most struck by Picasso's project for a monument to his friend Guillaume Apollinaire. 'Loads of triangles,' he said. 'It almost looked like a climbing frame.'

'I've never painted anything,' Picasso once said, 'but what I've seen and felt.'

Caroline Burke-Gaffney, with her daughter Emma, a final-year student at Wimbledon College of Art, was looking at the figure of the Little Girl Skipping, with a basket for a stomach and a pair of platform shoes. They were both smiling. 'There's almost nothing here you don't look at and get a reaction within yourself,' said Emma's mother. 'Those shoes remind me of my daughter, who's shoe-crazy. There's a lovely fish on a bit of newspaper, it reminded me of holidays in the South of France. And there's a wonderful guitar, further down, you can hear music coming out of it. You can. Can't you, Emma?'

By the next room Picasso was in his seventies, and his works were more child-like than ever. There was a sculpture of a man represented only by pieces of wood shaped like an easel, so roughly nailed that the wood, in places, had split, with a wooden phallus - a self-portrait, perhaps. The sculptures now were almost hieroglyphics, even scarecrows. But a child could still see what they were. There was a man's head made of an empty orange box, with a wooden chip for a mouth and two trouser buttons for eyes.

When he was a child, Picasso cut out animals to amuse his small cousins. At 80, he had shrugged off the academic brilliance of his youth and returned to cut out fat old men instead. His audience is still amused. The faces pouring out back down the streets away from the Tate looked like a crowd that had just come from a good play in the West End, smiling, enlivened or, like seven-year-old Benjamin Day, emboldened.

'Picasso: Sculptor/Painter' is at the Tate until 8 May. Advance booking: 071-396 4567. pounds 6.25 to book or pounds 4.25 for OAPs and the unemployed. Tickets at the door pounds 5 or pounds 3.

(Photograph omitted)