According to Polling (2010), what are some issues with the use of PR schedules to evaluate reinforcer potency, generally and with applied populations specifically

answer; the best answer is (demand);

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.