Which category of vocal behavior is seen as modifications of all vocal cues that accompany spoken words?

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.        

probably 3 since archeologists and historians don’t understand there writing.