If design is everything "from the spoon to the city", as the Italian architect Ernesto Rogers put it in 1952, writing about design tends to gravitate towards the larger end of the spectrum. After all, there's not much to say about a spoon. Or is there? I've found myself thinking about cutlery twice in recent months. The first time was in an airport restaurant as I tried to hack my way through a steak with a serrated butter knife. Here, the security protocols of post-9/11 airports were getting in the way of a good meal.

The typographer Adrian Frutiger once remarked that "If you remember the shape of your spoon at lunch, it has to be the wrong shape." Frutiger was referring less to instances where the cutlery was literally the wrong shape – as my knife was – than to those where the designer had styled it to be more memorable. He believed that spoons, like letters, were merely tools – "one to take food from the bowl, the other to take information off the page". For the diner or reader to be comfortable, the cutlery or typeface has to almost disappear. For modernists like Frutiger, there was a morality to design: every function had a perfect form, and to exceed that with some expression of ego was to stray into decadence. The critic Reyner Banham put it succinctly: "There is almost nothing a designer can do to, say, a spoon, a cup, a rolling pin, a wine glass or a broom, except fuck it up."

The conservative, almost unchanging nature of cutlery design shows that, while we are open to all sorts of culinary experimentation, we are intolerant of any extra interface between us and our food. I spoke to Alberto Alessi, who has commissioned some of the best-known cutlery sets of the 20th century (in so far as any cutlery set is well known), and he said: "It is very difficult to modify tradition. Maybe in two or three cases we've had a designer who had the courage to change a fork from four tines to three – and it was really dramatic." One such set, with a three-tined fork and curvaceous handles, was designed by the architect Jan Kaplicky. It didn't sell.

Although we all think we know what a fork and a spoon look like, designing one is somehow far from straightforward. Jasper Morrison once joked that it took him four years to design a fork, whereas a spoon – known as "the face" of the cutlery set – is easier. The spoon you have in your mind is an archetype, one that Alessi describes as "a clear representation of the maternal code". Spoons, you see, are embedded with our memories of being fed as children. Knives and forks, on the other hand, belong to the paternal code.

Changing shape of cutlery ... Mickael Boulay's set of forks, designed to help hemiplegics develop their motor skills

But not all forks and spoons are archetypes, which brings me to the second occasion lately when I found myself thinking about cutlery, rather than just shovelling food with it. I was at the Design Academy Eindhoven earlier this month, and one of the graduating students had designed a cutlery set for people with hemiplegia – a paralysis of one side of the body. Mickael Boulay's concept was to create a set that can help the patient develop his or her motor skills. Working with a young hemiplegic, he created four sets – one for each stage of development. The first two sets are strange globular things, like palaeolithic tools with a space-age finish. Designed to be easy to grip, the fork resembles a toy elephant, and serves merely to steer the knife between its two front legs, or tines. As the patient's skills develop from a fist-grip to a finger-grip, the cutlery evolves into much more recognisable forms.

Boulay has this encouraging idea that "the human body is like plastic", and that just as we can become disabled, we can "unbecome" disabled. The adaptability of the human hand, even the partially abled one, is written into his cutlery set.

Alessi also tells a story about that adaptability. When he approached Achille Castiglioni to design a cutlery set for him in 1980, the Milanese maestro held a hexagonal pencil between his fingers to demonstrate that the hand is "designed" to be adaptable to all sorts of forms, and that functionalists had taken things too far. Castiglioni's set, called Dry, had unorthodox square handles and was extremely popular – though not as popular as another maestro's a few years later, Ettore Sottsass's Nuovo Milano cutlery, whose handles were designed to be "like a stone polished by the sea".

The question raised by Boulay's set is whether it would appeal to a non-hemiplegic customer. Would the association with disability turn people away, or would it open our eyes to the possibilities of eating with something other than an archetype? Indeed, the fact that we still use these ancient implements for pronging and slicing made me realise how little things change. The personal fork has been around since 4th-century Byzantium (although it didn't arrive in Britain until the 16th century). I wonder how long it will be before it is superseded by a new archetype. Will it be defined by a change of diet, or is the food we eat defined as much by our cutlery?