Answer
The independent variable is inhaled oxytocin or inactive placebo. The dependent variable is if they gave their money to a trustee or not.
Work Step by Step
The independent variable in a study is the one that is manipulated. So in this study, participants either inhaled oxytocin or a placebo. Since that is an either/or you know it is the independent variable. The dependent variable is the one that is caused by the change in the independent variable. Here they were measuring how much money was given to the trustee - that's the dependent variable that should differ based on if they inhaled oxytocin or not.
