Public opinion is difficult to measure because

any public issue likely has separate groups with their own views

people disagree about which public issues are important

few issues capture all of america's attention

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

im sorry i wish i can but try google