In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.
One example: Article: Homework can put you in a badmood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay.
Answer: whether mood affects their learning ability
Solution is here: Researchers did experiments on kids in order to find out _ .
Explanation: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment.

Now, solve this: Article: Man-made nighttime lights have appeared everywhere in industrialized countries over the last century.What people are now asking is whether exposure to lightened darkness can affect the brain. To find out,Tracy Bedrosian,a doctoral student in neuroscience at Ohio State University,placed hamsters into two environments.In one,they were exposed to 16 hours of daylight and eight hours of complete darkness each day.In the other,the animals experienced 16 hours of daylight,but at nighttime,a dim light was kept on,at about the intensity of a TV screen lighting a dark room. After eight weeks,the researchers tested the hamsters for behavior that would suggest they were depressed.For example,they looked to see whether the hamsters still engaged in activities they normally enjoy,such as drinking sugar water. In people,loss of enjoyment is a major symptom of depression. Hamsters in both groups were given a choice between drinking tap water or sugar water.The hamsters exposed to light at night drank similar amounts of tap and sugar water----they'd lost their preference for the sweet treat. These changes in behavior were associated with changes in a brain region known as the hippocampus .The hamsters exposed to night light had a reduced number of so-called dendritic spines on the surface of cells in this region.These spines are hair-like things that stick out,and that brain cells use to communicate with one another. The findings match up with studies on humans that have d the hippocampus to be involved in depression. A patient with major depression has a smaller hippocampus. The brain changes in the hamsters might arise from fluctuations in the production of the hormone melatonin . Melatonin signals to the body that it's nighttime,but a light at night dampens its production. The hormone has been shown to affect mood,and so a decrease in melatonin might prompt depression,Bedrosian says. If the same mechanism is at work in people,then "people might want to try to avoid falling asleep with their TVs on at night,or to try to minimize light exposure during the night," she adds.
Answer: see whether lightened darkness affects the brain
Solution:
the experiment was done to _ .