Professor Hebb Is Studying Whether Learning Is Affected by Different

Multiple Choice

Professor Hebb is studying whether learning is affected by different environments. He raises some rats in cages with many interesting objects to play on and explore, and other rats in isolated, barren cages with none of the interesting objects. Later, Hebb carefully records how many attempts it takes each rat to learn to run a maze with no mistakes. What is the independent variable in this study?

A) how many attempts it takes each rat to learn to run a maze
B) being raised in an interesting or a barren environment
C) use of animals versus people
D) number of rats in the study