While the innate quality of the European students was very high, for the most part their study habits were frightful.

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Several years ago, Wrigley and The Princeton Review surveyed American and Canadian college students about their study habits and found that of the students who chew gum while studying for exams, 41% do so to combat stress while 23% do so to increase concentration.

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Another saw the use of a robot sage grouse hen to study their real-life mating habits.

CNN: April 4, 2012 -- Updated 1350 GMT (2150 HKT)

Everyone taking part in the study was asked about their eating habits and their health was monitored for a decade.

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The focus was on their exercise habits and eye health rather than being a scientific study of eye cells.

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The new study questioned 2, 513 people in the US about their online habits.

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