An experiment involves the manipulation of the dependent variable by the experimenter

After playing a violent video game, ten-year-old Craig's father tells him it is past his bedtime. Rather than using his usual mild complaints, Craig responds with anger and noncompliance. It is likely that playing the video game

A) altered Craig's cognitive schemas. B) decreased Craig's emotional responsiveness. C) desensitized Craig to his father's directives. D) increased Craig's arousal level.

A guiding principle of understanding human development is that it is best studied using the methods of:

a. philosophy b. introspection c. culture d. science