At most times in most cultures, men have worn their hair in styles that are different from women's. American sociologist Rose Weitz once wrote that the most widespread cultural rule about hair is that women's hair must differ from men's hair. An exception is the men and women living in the Orinoco-Amazon Basin, where traditionally both genders have worn their hair cut into a bowl shape. In Western countries in the 1960s, both young men and young women wore their hair long and natural, and since then it has become more common for men to grow their hair. During most periods in human history when men and women wore similar hairstyles, as in the 1920s and 1960s, it has generated significant social concern and approbation.