In a study of the impact of public service announcements (Spa’s) on attitudes toward smoking, researchers gave participants a pre-test which measured their attitudes toward smoking in public spaces. Participants were then exposed to 3 Spa’s regarding second hand smoke interspersed in a half-hour television program. Following that program participants were asked to complete a post-test that

measured their attitudes toward smoking in public spaces. Given the short time between completing the identical instrument on attitudes toward smoking in public spaces, what is the most likely threat to the internal validity of this experiment?

a. Observer Bias
b. Experimenter Bias
c. Testing effect
d. Maturation

Answer c