Another headline pops up: "Scientists aim to make computer that thinks like a human". And I think no, No, NO! Don't, whatever you do, do that. Even if Ray Kurzweil is the one suggesting it's coming.

Why don't I like the idea of a human-like computer? Am I creating a silicon ceiling beneath which I'm trying to keep our processing friends?

Actually, no. I just think that humans are a terrible example to follow if you want to develop something that's conscious – which is generally what these efforts to create "human-like" systems are really about: to reach the point where the machine says "I am", and everyone falls about, stunned.

My reasons are simple. We don't build skyscrapers based on the same principles as the human spine; if we did, then they'd be constantly falling down or showing signs of significant weakness. We don't build transport systems that work like the human body, using muscle-like elastic bands snapping back and forth to power them. We don't build cameras where the wires taking the signal from the CCDs runs in front of the CCDs themselves.

Humans, though, are built like that. The spine is well-suited for hanging a lot of organs off in a four-footed beast; but pretty badly adapted for bipedal, upright walking, because all the stresses are put in places where, over the course of years, they'll mess things up. Our relatively newly acquired Achilles tendon is a significant point of weakness during running (ask anyone who's snapped one of theirs). The retina is a model of daft design, with all the blood vessels passing in front of the rod and cone cells. That we're not aware of this is a tribute to the brain's ability to filter data.

Haphazard construction

That's the thing: evolution is a terrible designer. What it's good at (supremely good, of course) is finding what works best at a particular point in time in a particular environment. And the same applies with the workings of the human brain. This idea is wonderfully set out in a book called Kluge: The Haphazard Construction of the Human Mind, by Gary Marcus. He's professor of psychology at New York university, and examines carefully how the workings of our minds – not just brains – are as evolutionarily messy as our spines, tendons and eyes.

The chapter headings give you a flavour: memory, belief, choice, language, pleasure, things fall apart; and true wisdom.

For instance, when it comes to deciding what to do, Marcus argues that we have two systems operating in our minds: an "ancestral" system and a "deliberative" one. We've had the ancestral system for hundreds of millions of years, dating back before we came down from the trees (before "we" were "we", in fact). The deliberative system requires something closer to language; it's younger, and it and the ancestral system frequently disagree and fight like two cats in a bag. The older one, being better wired into our subconscious, often gets the upper hand.

Take the real example Marcus describes of a Chicago law firm which, trying to drum up business, paid for a 48-foot three-panel billboard with "the torso of an exceptionally attractive woman, breasts all but bursting out of her lacy black bra; the torso of a man no less handsome, shirtless, with his well-oiled muscles bulging; and, just above the law firm's name and contact information, a slogan containing just five words: LIFE'S SHORT - GET A DIVORCE".

Now, divorce is expensive, emotionally damaging, time-consuming, and can take years to recover from. Your deliberative system knows that (or has read about it). Yet you can be sure that at least some of the married people who saw that billboard heard a small internal yelp – their ancestral system saying "I'm missing out on hot sex!" Both pieces of knowledge are part of your mind. But why is the ancestral system even saying it? Can't the deliberative system hold it down? It turns out that no, it can't.

Marcus also has an example of incest that causes no harm but which leaves you wanting to wash your brain out and at the same time wondering why. It's a strange journey looking into the bizarre workings of your mind.

Irrational decisions

Similar problems circle around us every day. It's part of the reason why we need politicians: we need people who can find ways to use language in order to keep both our deliberative and ancestral systems feeling sated. People (never you or me, of course) make irrational decisions about all sorts of things: houses, clothes, cars, beliefs, money. Countless studies show that the human mind just doesn't work in a rational manner. Douglas Hofstadter, who is very much cleverer than anyone in pretty much any room, puts it another way: research to create computer models of the mind "helps remind me of the immense subtlety and elusiveness of the human mind".

Well, yes, "elusiveness" is one way of putting it, I suppose.

And yet we're keen to have computers that will mimic this? The thought makes me shudder. The much-missed Douglas Adams had it absolutely right throughout The Hitchhiker's Guide to the Galaxy, where his "humanised" machines always suffered terribly for their "elevation" to our level: Marvin the Paranoid Android with his brain the size of a planet, who couldn't bear performing the menial tasks that his masters with their inferior intelligences demanded of him. (It would be like us being ordered about by our dogs.)

Or the intelligent lifts – aka Happy Vertical People Transporters: "Not unnaturally, many elevators imbued with intelligence and precognition become terribly frustrated with the mindless business of going up and down, up and down, experimented briefly with the notion of going sideways, as sort of an existential protest, demanded participation in the decision making process and finally took to squatting in basements sulking."

Is that really the sort of computer you're looking for? Because if it is, then I think we've got problems far bigger than the ones that people are trying to solve with these systems.

No; while it's certainly interesting to ponder what might constitute machine consciousness, to try to create human-like "machine minds" is a mistake, and any attempt to reverse-engineer our jumble of evolutionary leftovers and stick it into a machine would be an act of amazing cruelty. Apart from anything, would you really want a machine that could remember what it did a month ago, but can't remember where it put that file it saved five minutes ago? Or can remember that it fed the dog, but not what it had for lunch five days ago?

Let's get off that rollercoaster while we can. What we really want is machines that are as unlike humans as possible. We want them to be rational, predictable, fast. And most of all I want them to remember where I left my keys. Because I sure as hell can't.