Playing video games will improve individual spatial skills. what is the dependent variable in the experiment? a. playing video games b. type of subjects c. type of video game d. spatial skills

I believe the answer is: D. Spatial skills

Dependant variables refers to the variables which condition would be affected by other independent variables.  

Dependent variables represent the final output or outcome of the variation that is being studied. From the case above, 'playing video games' would be the one that considered to be independent variable while 'spatial skills' would be the one whose changes would be measured,