What is the independent and dependent variables?

Question

A linguistic anthropologist is studying the relationship between the ability to understand the mainstream culture’s humor and the number of years an individual born overseas has lived in the United States. A single ESL group was interviewed, shown 10 cartoons, and then asked to explain why those cartoons are considered funny by Americans. Is there a relationship between the numbers of years lived in the United States and the number of adequately explained cartoons?

I need to know which variable is the independent one and which is the dependent one. 

Answer 1

Understanding seems to depend on length of time immersed in the U.S. 'culture'.