It was not, he notes, because of new technology but because the scientific community organized itself differently and allowed machines to take over most of the mechanical work.

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One expert on the scientific benefits of gratitude, Dr. Robert A Emmons, notes that feeling grateful can improve your health, your mental function, and your relationships with other people.

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Under cross-examination, Ms Barlow admitted she had not made notes at the time prompting defence lawyer Brendan Kelly QC to claim it was more "guesswork" than scientific fact.

BBC: April Jones