Social scientists often mention Puerto Rico as an example of how race is not conceived of in the same way in all cultures. It is said that people in Puerto Rico do not see race in the same way as people in the United States. In the United States, people tend to see race as a very strict dichotomy. A person is white or black with nothing in between. It is said that people in Puerto Rico see race on a continuum of colors, not in separate categories.
In addition, Puerto Ricans are said to use social class to help determine what race a person is. In the US, race and social class are separate concepts.
The fact that race is conceived of in a different way in Puerto Rico shows that race is a social concept and not a biological one.