It says a research group are studying pigs because they resemble human beings. They give pigs alcohol and let them drink freely. Pigs behave like humans. A herd of pigs also has their own social status. The pig that has the highest standing can choose to drink first. But as they drunk, their social standing would become lower. After pigs realized this, they consciously avoid alcohol!
I guess in respect of this, pigs are much smarter than humans.