Final answer:
The correct answer is option c) Word frequency.
Step-by-step explanation:
In the context of the AoA (Age of Acquisition) coglab experiment, the independent variable is c) Word frequency. The independent variable represents the factor that researchers manipulate to observe its effect on some outcome, which is known as the dependent variable. The dependent variable would be the reaction time, as it is what would be measured in response to changes in the independent variable.
The independent variable is chosen by the experimenter and is typically the variable of interest in an experiment. In this AoA experiment, word frequency is manipulated to see how it affects the reaction times of participants when they perform a cognitive task. The values of the independent variable are set before the experiment takes place and are not influenced by other variables in the experiment, distinguishing it from dependent variables which change in response to the independent variable.