Answer:
The emotional or neutral word list
Explanation:
In a psychological experiment, an independent variable is one which can be manipulated and can be controlled by the experimenter or the researcher. Whereas a dependent variable is that variable which can be measured by the researcher or the experimenter.
In case of independent variable, the experimenter can change the variable and these variables have a direct effect on the dependent variable. While the dependent variable is assumed to be "dependent" on the independent variable.
In the context, the list of emotional word or the neutral words are the independent variable as Dr. Jeffries can manipulate or the change the words that is given to the participants.