In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.
Q: Article: People who smoke could lose around one third of their daily memory, researchers say. A study by a team at Northumbria University showed that smokers lost more of their memory when compared to non-smokers. And the research also found that those who kicked the habit saw their ability to recollect information restored to almost the same level as non-smokers. The study involved more than seventy 18-to-25-year-olds and included a tour of the university's campus. Those who took part were asked to recall small details, such as a list of songs played at a campus concert and tasks completed at various points-known as real world memory test. Smokers performed badly, remembering just 59 percent of tasks. But those who had given up smoking remembered 74 percent and those who had never smoked recalled 81 percent of tasks. Dr. Tom Heffernan, who leads Northumbria University's Collaboration for Drug and Alcohol Research Group, said the findings would be useful in anti-smoking campaigns. He said, "Given that there are up to 10 million smokers in the UK and as many as 45 million in the United States, it's important to understand the effects smoking has on everyday cognitive function-of which prospective memory is an excellent example. " "This is the first time that a study has set out to examine whether giving up smoking has an _ on memory. We already know that giving up smoking has huge health benefits for the body, but this study also shows how stopping smoking can have knock-on benefits for cognitive functions too. '' The research will now investigate the effects of passive smoking on memory, while Dr. Heffernan and Dr. Terence O'Neil will look into the effects of third-hand smoking-toxins left on curtains and furniture.
Answer: Smokers are compared to non-smokers.
A:
What's the main idea of the passage?