Blockhead

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 entitled Psychologism and Behaviourism. In this paper, Block argues that the internal mechanism of a system was important in determining whether that system was intelligent, and also 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 correct 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. Although the number of sentences required for a 30 minute conversation is said to be greater than the number of particles in the universe, it is clear that such a machine could at least logically exist (this makes for a purely theoretical argument which can't be applied in practice). From this, Block leads us to see 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 similar to John Searle's Chinese Room.