The data they rely on – arrest records, postcodes, social affiliations, income – can reflect, and further ingrain, human prejudice.
 The promise of machine learning and other programs that work with big data (often under the umbrella term “artificial intelligence” or AI) was that the more information we feed these sophisticated computer algorithms, the better they perform.
 Last year, according to global management consultant McKinsey, tech companies spent somewhere between $20bn and $30bn on AI, mostly in research and development.
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 The program was never given a definition of a human face or a cat; it had observed and “learned” two of our favourite subjects.
 Tay, Microsoft’s artificial intelligence chatbot.
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 Photograph: Microsoft This sort of approach has allowed computers to perform tasks – such as language translation, recognising faces or recommending films in your Netflix queue – that just a decade ago would have been considered too complex to automate.