Answer:
independent variable
Step-by-step explanation:
Independent variable: In psychological experiment, the term "independent variable" is described as a specific variable that is being controlled, altered, or manipulated by an experimenter or researcher or investigator to see its effects on the dependent variable. Independent variable has a direct effect on the dependent variable, so any changes in the independent variable will effect the dependent variable directly.
In the question above, the amount of light in this investigation is an independent variable.