Okay.
We conducted an experiment to see if negative election ads evoke different reactions from people, as compared to the ads that we researchers call “promotional advertising” and that you just called “positive advertising”. Instead of attacking its adversaries, the party promotes its platform, record or team. We found that people responded to negative advertising with heightened attention. Their pulse quickened.
We measured people's pulse, as well as cutaneous sweating. We also asked people to spontaneously indicate their first impression after each ad. We refer to that as “spontaneous cognitive responses”. This method is very commonly used in social psychology to measure people's level of cognitive engagement.
We realized that election ads, especially ads that attacked the party that the elector supports, triggered cognitive processes to protect the ego. People tried to find arguments to destroy the negative argument that was presented. Based on the increase in skin conductance and pulse, we realized that people responded more intensely to negative ads.
In short, that is what we concluded from that work. The type of ads people are exposed to triggers different physiological and cognitive reactions.