1.1.53 Researchers studied 650 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the winter. The study also found that those born in the spring were less likely to be irritable, while those born in summer were less likely to be exessively positive. What is the research question the study adresses?