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Scientists have developed an IQ test for dogs they say could lead to a greater understanding as to how human health is linked to intelligence. Studies have shown that cleverer people tend to live longer. Rosalind Arden is a research associate at the London School of Economics who has co-authored this new study. She tells Dan Damon about her research. (Image: Petra, the Alsatian dog from the Â鶹Éç's children's programme, 'Blue Peter', answering her fan mail. Photo: John Pratt/Getty Images)