Today, the best backgammon programs are arguably as good as the top human players and all are self-teaching systems based on neural networks.

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Dr Mozer's household-control system consists of a number of different neural networks, each in charge of one aspect of his domestic economy.

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Its reaction with the odour molecules changes a detector's electrical resistance, and this signal is fed into a neural net (the closest that computer technology has got to imitating the pattern-recognising abilities of networks of nerve cells) to work out what is being smelt.

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