Blockhead (computer system)

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Blockhead is the name of a theoretical computer system invented as part of a thought experiment by philosopher Ned Block, which appeared in a paper titled Psychologism and Behaviorism (though Block does not name the computer in the paper). In this paper, Block argues that the internal mechanism of a system is important in determining whether that system is intelligent, and also claims to show that a non-intelligent system could pass the Turing test.

Block asks us to imagine a conversation lasting any given amount of time. He states that, given the nature of language, there are a finite number of syntactically and grammatically correct sentences that can be used to start a conversation. From this follows the point that there is a limit to how many "sensible" responses can be made to this first sentence, and then again to the second sentence, and so on until the conversation ends.

Block then asks us to imagine a computer which had been programmed with all these sentences—in theory if not in practice. From this, Block argues that such a machine could continue a conversation with a person on any topic, because the computer would be programmed with every sentence that it was possible to use. On this basis, the computer would be able to pass the Turing test despite the fact (according to Block) that it was not intelligent.

Block says that this does not show that there is only one correct internal structure for generating intelligence, but simply that some internal structures do not generate intelligence.

The argument is related to John Searle's Chinese room.

A recent objection to the Blockhead argument is Hanoch Ben-Yami (2005), who agrees that Block's machine lacks intelligence, but compares its answers to a poetic dialogue (in which one man is whispered romantic poetry to recite to his would-be lover), as it only answers what it has been told to answer in advance by its programmers.