Fear can be fun. Many young people queue up to ride very fast and scary (嚇人的) roller coasters, screaming but enjoying themselves. Other people like to read "goose bumps" (雞皮疙瘩) books or watch horror movies (恐怖電影) at night, scared to death but feeling excited. Why do people like being scared? 

    Fear is an ancient way of surviving. Being scared makes animals (including humans) flee (逃走) from danger and save themselves.It is because of fear that we have lived through millions of years of evolution. Those who lacked a strong fear response (反應) were more likely to be killed, leaving the more timid and careful to pass their genes (基因) onto the next generation. 

    How do scientists explain why shivering (顫抖) over such scary things is fun? 

    Some kids will go to a scary movie and love it and laugh over it, others will feel anxious and hide their faces and some won't even set foot in the cinema," said Ned Kalin, a US scientist. "Which kind of person you are depends partly on experiences you've had and partly on your genes." 

    What happens in the brain when something frightens you? 

    Nerves (神經) that begin at the eyes and ears lead to a part of the brain called the amygdala (類扁桃體). When you suddenly see a snake, for example, the amygdala makes you freeze, perspire (流汗), have a quickened heartbeat, or run very fast. 

    However, seeing the snake also uses another part of the brain, the cortex (皮層). It analyzes (分析) the situation, and if it finds that the snake is only made of rubber it tells your heart and the rest of your body to calm down. Think of the amygdala as the engine and the cortex as the brake. 

    Back to the first question: Why do some people like to make themselves scared? 

    One reason is that we can play games with fear, find ways to reduce the scariness by looking away or thinking of something else," Kalin said. "To believe we have control over a situation gives us a feeling of power. 

    "Scary movies or novels are good practice to prepare young people for the real thing. Thrills (顫抖) such as roller coaster rides also go to the brain's pleasure centre. 

    And there might be some evolutionary advantage to being able to adjust this system that is there to protect people.