ExperimentControlled experiment (negative control)...To put it simple,Will A's heart beat fast when together with B?this is the objective of the experiment you're conducting now.We've measured his normal heartbeat rate already.That is what we call a controlled experiment.A pets B's head at close range.Not that.High heartbeat rate!To find out, it is necessary to compare with the result of the 「experiment of the situation when B is not present」.Umm... Ibarada-senpai,what do you mean by controlled experiment...?Now, let's compare with the experiment when 「A is doing nothing」.A does nothing.I mean the person as a variable.Heart rateThis is called a negative control,Heart ratea contrastive experiment where we carry it out to compare knowing that nothing will happen.Comparison