While studying the impact of ginkgo biloba on memory, a researcher has one group of rats on a normal diet while the other rat group is given measured doses of ginkgo biloba with their meals. While observing the rats run a complicated maze, the researcher notes that the ginkgo biloba-enhanced rats’ maze is more brightly lit than the normal diet rats’ maze. The difference in lighting in this study is a(n) ______.

In a scientific study or experiment, the variable being tested or measured or affected by the experiment is called the dependent variable. The independent variable is the variable that is not dependent on any other variables or factors. It is changed or controlled during an experiment in order to cause a change in the dependent variable.

Here, the study is conducted on rats to observe the impact of ginkgo biloba on rat's memory when a measured dose of the same is given through their diet. Ginkgo biloba helps to retain short-term spatial memory in rats. Rats are comfortable in the light and get used to any lighting situations. But they avoid light due to their nature and are generally nocturnal. They cannot see properly in the dark, but can easily navigate through the darkness with the help of their extremely sensible whiskers. The difference in lighting during the experiment acts as an independent variable that is manipulated to induce a change in the dependent variable, to check the ability of ginkgo biloba-enhanced rats and normal diet rats that run through a complicated maze.