issue 31.Money spent on research is almost always a good investment, even when the results of that research are controversial.

　　argument 187.The following appeared as part of an article in a health magazine. A new discovery warrants a drastic change in the diets of people living in the United States. Two scientists have recently suggested that omega -3 fatty acids play a key role in mental health. Our ancestors, who ate less saturated fat and more polyunsaturated fat, including omega -3 fatty acids, were much less likely to suffer from depression than we are today. Moreover, modern societies ― such as those in Japan and Taiwan ― that consume large quantities of fish report depression rates lower than that in the United States. Given this link between omega -3 fatty acids and depression, it is important for all people in the United States to increase their consumption of fish in order to prevent depression.