The so-called maturity refers to the process of the subject's own growth in the natural state. Including both physical and psychological aspects.

Historical factors mean that the past behavior of the subjects may have an impact on the present experiment.

Secondly, let's talk about this experiment again. The subjects were divided into two parts through the comparative experiment of fixed group. In this process, only the experimental treatment is different, and the two experience the same time, otherwise we assume the same. The premise of the experiment is also assumed like this. You have to understand that as long as we don't find significant differences before the experiment, it's all the same. But this is not a strict experimental design, so this is a fixed group without pre-test.