I thought an important feature of the Turing test was that the situation was exactly equal for each contestants, human and computer. The interrogator communicates with each using a teleprinter. Turing in his 1950 paper when talking about the interrogator communicating with player A in the imitation game: "The ideal arrangement is to have a teleprinter communicating between the two rooms [interrogator's and player A's]" then in the next para: "We now ask the question, 'What will happen when a machine takes the part of A in this game?'".

So there's one teleprinter in the human's room and another in the computer's room, and the interrogator types the questions on their teleprinter and gets printed responses back from the contestants. Everything is equal except one contestant is a human and the other a machine.

But the computing machine has no sensory apparatus. It can't see the questions printed by the teleprinter in the computer's room. If it can't see the questions then it can't understand them. In fact the computer must be wired directly into the interrogator's teleprinter, and the computer gets voltages - not words. The computer might have its causality defined by a human programmer (by programming the computer) such that the computer sends voltages back to the interrogator's teleprinter and words are then printed by it, but still, the computer gets voltages, not words.

Since the causality of the computer is defined by the human programmer, doesn't that mean that the Turing test, as Turing describes it, actually tests the intelligence of two humans, the human contestant and the computer programmer?

  • "But the computing machine has no sensory apparatus." - create a robot with cameras, image from which is handled by the AI. Well, in order to [artificially] create a great intelligence ones the creators themselves should be very clever.
    – rus9384
    Commented Aug 1, 2018 at 0:12
  • Yes, a robot with human-like sensory apparatus should be the computer contestant, but there is still the question of to what extent the behaviour of the robot is dictated by the human programmer. Even with a robots whose causation is defined or largely defined by a human, the TT is still testing the intelligence of two humans isn't it?
    – Roddus
    Commented Aug 1, 2018 at 0:30
  • It's hard to say if it's simpler, harder or exactly as difficult to create an intelligence as good (or bad) as one's own. But if the third variant is false, the test will be unfair comparing intelligence of the creator and the contestant.
    – rus9384
    Commented Aug 1, 2018 at 0:35
  • You have my vote, The Turing test tests the ability of programmers to pass it. If the programmer cannot pass it then they are not going to be able to build a machine that does. Suppose as the human I were to ask 'What makes you angry'. Nothing would, obviously, so to pass the test the machine would have to be programmed not to answer questions as an honest human being would. I suspect that it's generally agreed these days that it is not an effective test of anything more than the programmer's skill at deception, but I may have just stumbled on a few unrepresentative articles.
    – user20253
    Commented Aug 1, 2018 at 11:46
  • Empirically, it's easy to write a program with unexpected behavior. It's also possible to write a machine learning algorithm (like an artificial neural net) that mere humans can't figure out, because the knowledge is expressed as a collection of numbers bearing no obvious relationship to what the machine is doing. It's possible to write a program with unexpected and highly useful behavior, such as template metaprogramming in the C++ language. Commented Aug 1, 2018 at 15:02

5 Answers 5


The Turing Test is perhaps best understood as a thought experiment aimed at answering the question "if something purely mechanical could display all the perceptible signs of consciousness/intelligence, would there be any valid reason to deny it possessed those qualities?" Or, to put it perhaps more correctly, "is there any meaningful definition of intelligence other than 'able to display the empirical signs of intelligence?'"

Turing's own answer is "no." Who constructs the machine, and the details of how the machine communicates with the world are peripheral to Turing's aim, which, beyond the immediate question above, is to demonstrate that human intelligence itself admits a purely mechanical explanation, it doesn't require any mystical or supernatural soul to animate it. Turing isn't primarily concerned with the competitive aspect of the Test, it's merely a vehicle for this idea.

The Turing Test is most easily understood in a larger context of the 20th century British and American philosophical push towards redefining all concepts solely in terms of their empirical traces. There are many people who reject this, and for a variety of reasons. Most criticisms of the Turing Test, including your own, are perhaps best understood as disagreements with Turing's (still controversial) fundamental assumptions (since any practical quibbles about the implementation of his test are largely irrelevant to his larger point). He did anticipate some of these disagreements, and formulate replies, you may find those of interest.

  • You say Turing seeks to show “human intelligence itself admits a purely mechanical explanation”. Do you mean behavioral explanation? Intelligence as internal process/structure (the common concept) might still be mechanical with no implication of behavior. My problem with intelligence-as-behavior is it fully fails to explain the inner processes/structures that yield human-like general intelligence, and without that knowledge, how could AI create genuine machine intelligence? Doesn't accepting any process/structure that yields some intelligent behavior just avoid this problem?
    – Roddus
    Commented Aug 3, 2018 at 0:02
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    I'm not defending Turing's position, just trying to explain it. He believed that intelligence itself would eventually be shown to be an artifact of a Turing Machine. Towards that end, he sought a redefinition of intelligence wholly in terms of its outward signs. Your objections are rejections of Turing's position, they cannot be reconciled with it. Commented Aug 3, 2018 at 13:17
  • Yes, Turing wasn't trying to explain intelligence as commonly conceived (i.e., something internal) but to redefine the meaning of the term "intelligence". He says as much in his 1950 "prediction": "Nevertheless I believe that at the end of the century the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted". Which isn't a prediction but a redefinition. How can redefining "intelligence" as behaviour explain how to make a machine intelligent? Doesn't the TT let AI dodge this?
    – Roddus
    Commented Aug 3, 2018 at 22:56
  • It's a basic philosophical disagreement. For someone like Turing, the talk of something "internal" is incoherent anyway. Just as new definitions of logical operators cleared away centuries of fuzzy thinking, and paved the way for a science of logic, he thought he could do something similar for the concept of "intelligence" by redefining it. Commented Aug 6, 2018 at 13:39
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    @Roddus Not everyone finds Turing compelling, and for those who don't, your line of argument is entirely typical. This is a central and live debate in the fields of biology, psychology, neuroscience and computer science as relates to the brain, the mind and the intellect. // With that said, I'm not sure there's much to be gained by simply repeating what --to be honest --were already the main objections to Turing at the time he first made his argument. Commented Aug 10, 2018 at 14:16

But the computing machine has no sensory apparatus. It can't see the questions printed by the teleprinter in the computer's room. If it can't see the questions then it can't understand them. In fact the computer must be wired directly into the interrogator's teleprinter, and the computer gets voltages - not words. The computer might have its causality defined by a human programmer (by programming the computer) such that the computer sends voltages back to the interrogator's teleprinter and words are then printed by it, but still, the computer gets voltages, not words.

Your thoughts are instantiated in electrical activity in your brain. So we know that a physical system that uses electricity can instantiate thoughts.

Now your brain receives electrical signals from your sense organs does stuff to those signals and sends other electrical signals to your muscles telling them what to do. So your brain receives signals, processes the information in those signals and sends out other signals. Your understanding of the world is a pattern of information processing.

The Turing machine is a universal computer - it can compute anything that can be computed by any other physical system and can simulate any other physical system to any desired level of accuracy. Your desktop computer can do the same operations as a Turing machine so it can also simulate any physical system, including your brain. So a computer that is programmed the right way and receives information similar to the information you receive can think in a similar way. And it won't just reproduce the appearance of doing the same thing, it can also simulate all the internal processes leading up to whatever thoughts you come up with. So it will think in the same way a human being thinks. We don't currently know how to write such a program, but the laws of physics say that it can be written.

See "Godel,Echer,Bach: An Eternal Golden Braid" by Hofstadter, "The Fabric of Reality" by David Deutsch chapter 5, and "The Beginning of Infinity" by Deutsch, chapters 5-7.

  • TM is a model much more powerful than any physical system due to unlimited memory.
    – rus9384
    Commented Aug 1, 2018 at 9:14
  • @rus9384 If a physical system runs out of memory you can add more. There is no known upper bound to how much memory you can add.
    – alanf
    Commented Aug 1, 2018 at 11:13
  • But you must add it, unlike in TM. In fact real computer is a 2-way finite automaton.
    – rus9384
    Commented Aug 1, 2018 at 12:44
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    No. Since memory can be added a real computer has the same repertoire as a Turing machine.
    – alanf
    Commented Aug 1, 2018 at 15:51
  • 1
    @alanf You're just waving your hands. You have no evidence you can build an infinite TM in the physical world. What you claim is contrary to known science.
    – user4894
    Commented Aug 2, 2018 at 9:12

Here is the question:

Since the causality of the computer is defined by the human programmer, doesn't that mean that the Turing test, as Turing describes it, actually tests the intelligence of two humans, the human contestant and the computer programmer?

The OP also mentioned the teleprinter that takes information as input from one side of the Turing test, processes it, and delivers information to the other side.

Note that both the teleprinter and the computer set up for the Turing test are very similar. Both input information, process information, and output information.

The two humans, contestant and programmer, have similarities as well regarding understanding. Regardless of whether the teleprinter or the computer under a Turing test understand anything when they process information, there is no doubt that these humans do understand language.

There are at least three reasons to remain hesitant about claiming that machines understand just as humans do.

First, John Searle in "Minds, Brains and Programs", where he presented his Chinese Room Argument, reprinted in Mind Design, pages 291-2), mentioned:

If strong AI is to be a branch of psychology, it must be able to distinguish systems which are genuinely mental from those which are not. It must be able to distinguish the principles on which the mind works from those on which nonmental systems work; otherwise it will offer us no explanations of what is specifically mental about the mental.

Second, Searle mentions in the same article (page 303) that what the computer, or the teleprinter, do when they "process information" implies that they have "a syntax but no semantics":

Thus if you type into the computer "2 plus 2 equals?" it will type out "4." But it has no idea that "4" means 4 or that it means anything at all. And the point is not that it lacks some second-order information about the interpretation of its first-order symbols, but rather that its first-order symbols don't have any interpretations as far as the computer is concerned.

Third, there is the the fallacy of anthropomorphism. Bradley Dowden describes this fallacy as:

This is the error of projecting uniquely human qualities onto something that isn't human. Usually this occurs with projecting the human qualities onto animals, but when it is done to nonliving things, as in calling the storm cruel, the Pathetic Fallacy is created.

Claiming that the computer understands as humans do because it processed information could be viewed as an example of the fallacy of anthropomorphism, or more specifically, the pathetic fallacy.


Bradley Dowden, "Fallacies", Internet Encyclopedia of Philosophy.

John R. Searle, "Minds, Brains and Programs" reprinted in Haugeland, J. (1981). Mind Design: philosophy, psychology, artificial intelligence (Mongtomery, VT, Bradford Books).

  • Searle makes an awful lot of assumptions, in addition to his constant begging the question in "Minds, Brains, and Programs". Uniquely human qualities? Exactly what's unique to humans? It isn't necessarily intelligence. Commented Aug 2, 2018 at 19:57
  • 1
    Bradley Dowden used the phrase "uniquely human qualities" in the last passage I quoted, not Searle. He was defining the fallacy of anthropomorphism. There are a lot of assumptions in strong AI. Here are two: (1) processing information makes something conscious, and (2) processing information is what humans do in their brains to make them conscious. Both of these need to be justified. In particular whatever models of information processing offered for consciousness need to be biologically plausible in terns the how neurons actually behave in humans. @DavidThornley Commented Aug 2, 2018 at 20:10
  • @FrankHuberry: Something makes people intelligent and conscious, and we don't know that it isn't possible on a computer. Unless you're an old-fashioned dualist, you must acknowledge that the brain is a physical device. Given that, it's conceivable that another type of physical device could do the same thing. Unless we know what consciousness is well enough to determine the mechanism(s), we can't say it's a "uniquely human quality". (Indeed, some animals do show intelligence, although we have no test for consciousness, so intelligence isn't uniquely human.) Commented Aug 6, 2018 at 17:00
  • We don't know that it is possible on a computer either. Having a link between what a computer does and what the human brains do is critical to claiming that a computer could be conscious by its "processing information". One of the problems is "biological plausibility". See Seanny123's question/answer on Psychology and Neuroscience SE for references on this issue: psychology.stackexchange.com/q/16269/19440 In general there is less problem with animals that have brains than there is with a computer. @DavidThornley Commented Aug 6, 2018 at 18:10
  • @FrankHuberry, Searle is attempting to show that turing machines and computers can't be conscious, and his reasoning is not sufficient to show that. Personally, I think it is possible to produce conscious computers that think and understand things, but here I'm just concerned with opposing Searle and noting that "uniquely human qualities" is very ill-defined. Commented Aug 9, 2018 at 17:24

You seem to be making two arguments here. Let me rephrase:

  1. A computer cannot see the words. It just gets voltages. Therefore, it cannot possibly understand the questions.

Response: Getting voltages is getting a kind of input. In fact, by your logic, you could argue we humans aren't seeing words either: we're just getting hit by light waves. But of course we are seeing words. And a computer is perceiving words as well ... just through a different sensory medium.

  1. It's the programmer that created the program. Therefore, any intelligence we attribute to the program when doing the Turing Test should really be attributed top the programmer, not the program

Response: Why would it matter how the program was created? You and I were created by our parents .. should they get the credit for our abilities rather than us? If I build a fast car, does that mean that the car isn't fast, because I built it? Of course that doesn't follow. Yes, I built it ... but it is also true that the car is fast. Likewise, if I create a computer program that is able to solve problems, make decisions, do reasoning, etc. ... should the fact that I created it mean that the program is in fact not doing any of those things? No. Of course, the question is whether I can create a computer program that has all these cognitive and mental abilities, but if I can, the fact that I did it does not take away from its abilities.

  • 1. Yes, maybe the interrogator's teleprinter is a sense organ of the computer. And "Getting voltages is getting a kind of input", which input to the computer is the output of the teleprinter. But in this case what is being sensed? Taking the keys to be in a keyboard, this sense detects press-release events at different locations within the keyboard, not words.
    – Roddus
    Commented Aug 3, 2018 at 2:13
  • 1
    @Roddus 2. Again, I largely agree: perception seems to be a really important aspect of intelligence and cognition; it is so much more than 'mere input', and likely much more closely integrated with other cognitive processes. For example, when we use imagination in order to think about something, we are presumably invoking perceptual processes. Intereestingly, however, the first AI people did not think perception was such a big deal at all. FAmously, Marvin Minsky put out a call for a graduate student to 'solve' perception as a one-summer project. :)
    – Bram28
    Commented Aug 4, 2018 at 0:55
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    2. (cont'd) Of course, perception turned out to be much harder than the original AI people thpught .... but does that mean it is not computational? Again, I think drawing that conclusin is premature. Maybe the computations are just a lot more complex than we think.
    – Bram28
    Commented Aug 4, 2018 at 0:57
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    @Roddus 3. Yes I mean his 1950 paper. Turing had absolutely no problem with the notion of learning machines. He was familiar with rhe work that had already been done with artificial neural networks, and had done research with them himself. In his 1950 paper, he explain that to many people, the idea of a machine that learns is paradocxical ( how can a machine learn ... i.e. Change its behavior ... if it is guided by a fixed program?) but explains how by differentiating between the (low) level of the program, and the (high) level of behavior, it is in fact easy to change behavior.
    – Bram28
    Commented Aug 4, 2018 at 1:03
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    @Roddus 3. (Cont'd) So again, to Turing, there is nothing paradoxical or problematic with the idea of a learning machine. In fact, there already were learning machines in Turing's time, and nowadays much of AI is all about learning (Deep Learning has been the big hubbub the last decade or so)
    – Bram28
    Commented Aug 4, 2018 at 1:06

I would like to address your main question "...how can the computer understand the interrogator?"
I am going to start by assuming that by "understand", you mean "communicate with."
Lets start with two isolated rooms 1 & 2. There is an input device (keyboard), and an output device (monitor screen), in each room.

First scenario:

Two humans, that understand English, each sits in front of a screen and keyboard.
The human in room 1 (H1) sends a message to human in room 2 (H2). Something like "what is your name?"
The human in room 2 (H2) responds "my name is (random name), what's yours?"

Second scenario:

Two humans, one understands only English (H1), and the other only understands Spanish(H2).
H1 sends the same message as before, but now in order to communicate with H2, there is a (E -> S) translator between H1's output and H2 input device. The same applies for the response from H2 going through a (S -> E) translator, so H1 never finds out he/she is communicating with a non-English speaker.

Third scenario:

Same as scenario 2 but he human in room 2 (H2) is replaced by a computer (Hal), and the translators are replaced with BCC(binary encoded characters) translators.
H1 sends the same message as before, and Hal responds with a random name. Again, H1 never finds out he/she is communicating with a machine.

The above should make it clear that communication between humans and machines (computers), is not a problem. All it takes is an appropriate "translator" so that they can communicate with each other.

Now, as to the matter of "understanding", at this time this is a quality that exists only in the human. However, progress in AI has come to the point that the human might be fooled into believing that he/she is communicating with another human, rather than a machine!

One final note. Although is true that the computer receives and sends "voltages", the presence and absence of these voltages form what is called a binary piece of information (a bit), and groups of them are encoded to form characters, and characters are grouped to form words!

  • You say, "I am going to start by assuming that by "understand", you mean "communicate with." Yet the idea of communication seems unclear. I press my garage door remote, it communicates with the door controller, the door opens. Neither remote nor controller has the causality of understanding. By "understands" I mean that a system contains a meaning of a shape, and this meaning is activated either by virtue of perceiving the external shape, or by the system directly identifying the shape - as with Chinese symbols entering the Chinese room. Though the Chinese room contains no meanings.
    – Roddus
    Commented Aug 9, 2018 at 10:45
  • First scenario: Two humans H1 and H2. Each understands the shapes caused (via the equipment) by the other. Second scenario: Three humans, H1, HT, and H2. HT perceives and understands the shapes caused by H1, then sends (mostly different) shapes to H2 that H2 perceives and understands. Third scenario: one human, one keyboard/screen, and one computer. H1 taps away on the K of K/S which transmits binary clocked voltages direct to C (no perception). C responds and sends clocked voltages back, which cause certain shapes on the screen of H1.
    – Roddus
    Commented Aug 9, 2018 at 10:46
  • I agree the K/S communicates with the computer but in the garage-door sense of "communicates". When we say humans communicate, we use a different sense that implies understanding and hence intelligence - but the garage-door sort implies neither. I agree that a human might be fooled by a system that has no understanding. Joseph Weizenbaum's 1960s ELIZA language simulator fooled quite a few people, as did Kenneth Colby's PARRY. I agree that hardware can be designed so that clocked voltages cause shapes that people understand.
    – Roddus
    Commented Aug 9, 2018 at 10:46
  • This is the reason I limited my answer to the "communicate" part. Not the "understand" part. You are right, your garage remote is "communicating" with the garage controller, but there is no "understanding" going on. Artificial Intelligence is trying to change that. It may take another 100 or 1000 years before the I-Robot machine becomes a reality.
    – Guill
    Commented Sep 2, 2018 at 3:42

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