The Turing test: the seminal experiment that questions our relationship with artificial intelligence

"Can a machine imitate human behavior?"

It was with this simple question that Alan Turing, mathematician and visionary, opened one of the most profound debates of the 20th century - and probably of the 21st too.

Today, with the explosion of artificial intelligences like ChatGPT-4 or 4.5, this question is resurfacing with new intensity. Some AIs are even said to be capable of "passing the Turing test", the mythical experiment designed to determine whether a machine can impersonate a human being. But what does "passing the Turing test" really mean? Where does the idea come from? And above all, is it still relevant today?

Let's take the time to go through it all together.

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The origins of testing: Turing's "imitation game

In 1950, Alan Turing published his now cult article Computing Machinery and Intelligence. In it, he proposed a daring reflection: instead of asking whether a machine can think, let's ask another, more concrete, more measurable question: "Can a machine imitate a human to such an extent that another human wouldn't know the difference?"

To introduce this idea, Turing first imagined an intellectual board game, which he called the "imitation game".

In this game, three people take part: a man (A), a woman (B), and a questioner (C), who can't see the other two and communicates only in writing. The aim is for C to guess who is the man and who is the woman. Meanwhile, A tries to fool C by pretending to be a woman, while B tells the truth.

Why this detour? Turing wanted to show how difficult it is to identify a person by language alone. If a man can impersonate a woman, then perhaps a machine could also impersonate a human.

And that's when everything changes.

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When the machine enters the scene: the birth of the Turing test

Turing then replaces one of the two humans with a machine.

The new objective of the game is: can the human judge tell the difference between a real person and a machine, solely through an online conversation?

If the machine manages to fool the human often enough - that is, at least 30% of the time, according to Turing - then it can be considered to be "thinking"... or at least, thinking well enough to simulate the human.

This is known as the Turing test.

But be careful: Turing wasn't saying that the machine becomes human. Nor even that it is conscious. Rather, he was proposing a pragmatic criterion for assessing whether a machine can reproduce human behavior from an external point of view.

It's a bit like testing an actor not for his experience, but for his performance.

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How is the test carried out today?

In its modern form, the Turing test often takes the form of an online discussion. One or more human judges chat blindly with two interlocutors: a human and a machine. All in chat or messaging mode. At the end, they are asked: "In your opinion, who was the human? Who was the machine?"

Sometimes, competitions are organized - like the Loebner Prize, which for years tried to reward the most convincing machine.

Some sessions last five minutes, others much longer. The longer and more complex the exchanges, the more likely the machine is to be unmasked. But conversely, if it responds quickly, well, with a dose of humor or even a little imperfection... it can appear surprisingly human.

That said, this test has its limits. It relies mainly on appearance, on form, not on substance. An AI can learn to give the illusion of understanding, without really understanding anything. It can imitate our tics, our syntax, our hesitations. But does that mean it thinks? The question remains open.

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ChatGPT-4 and 4.5: have they really passed the Turing test?

Today, new rumors are circulating: Open AI's GPT-4.5 is said to have passed the Turing test. In some experiments, participants even mistook the machine for a human in 60-70% of cases.

A UC Berkeley study, for example, found that GPT-4 was judged to be more human than... humans themselves. In this test, judges were more often wrong when identifying the AI than when they had to recognize other people.

In other words: GPT-4 no longer simply imitates a human. It can play the human role better than a normal human (in certain contexts).

But don't be too impressed. These tests assess theoutward appearance of intelligence, not its inner reality. GPT-4.5 is gifted for form: he responds quickly, understands context, makes jokes. But he doesn 't understand what he's saying the way a human understands an idea.

Above all, even humans don 't pass the Turing test 100% of the time. It's not uncommon for a human being to be mistaken for a machine, especially if he or she is shy, not very expressive, or awkward in his or her formulations. This says a lot about our standards, and sometimes about our prejudices.

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What's next? The big questions

If a machine can fool us just as well, then what's left that's specifically human?

This apparent success raises several fundamental questions:

• Does simulation mean understanding? Can an AI really think, or does it merely manipulate symbols without consciousness?
• Do we need to redefine intelligence? Is it a question of language? Emotion? Intuition? Consciousness?
• How far does illusion go? If a machine appears to be human, is that enough for us to grant it rights, responsibilities and trust?
• Is the Turing test still relevant? In the age of generative AI, other tests are being proposed: the Winograd test, which checks contextual understanding; or the Lovelace Test 2.0, which assesses creativity.

The line is blurring. It's no longer just a question of computing power. It's a question of philosophy,ethics and culture.

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The Turing test: symbolic, but not absolute

It's important to remember that the Turing test is not proof of intelligence in the strict sense. It's a starting point. A milestone in the history of our relationship with machines.

It assesses our ability to be deceived, not the machine's ability to understand.

And above all, even among us humans, we make mistakes. We project. We imagine. We interpret. An introverted person may seem cold to us. A fluid AI may seem warm. We're all biased by our expectations, our culture, our fatigue too.

So yes, GPT-4.5 "passes the test". But that doesn't mean it thinks, understands or feels anything. It only means that it's excellent at simulating.

And that's already huge.

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Conclusion: What the Turing test says about machines, and about us

The Turing test remains a seminal moment in the history of artificial intelligence. Not because it reveals an ultimate truth, but because it opens up a breach: it forces us to rethink our own criteria of thought, language and consciousness.

It's not just a test for the machines. It's also, in a way, a test for us. Are we ready to dialogue with entities that perfectly mimic humans, without being human at all? Can we still recognize what makes us unique?

AI moves fast. Very fast. But our understanding of what intelligence really is... may still be a work in progress.

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