Zombies can also be affected by emotions? ?

This is an older zombie movie. Because I have been watching "The Walking Dead" recently, I have little interest in the subject of zombies. After I watched it, I found out that this is a very old film. When there is no narration in it, there will be music playing. It turns out to be a bit cheerful and doesn't feel like a horror film. Looking at most of the bloody places, but the struggle between a few soldiers and scientists, in the last few minutes, it was very bloody, and the zombies became unusually brave and ferocious.
In fact, the most shocking thing is that the zombies still have feelings. When BUB discovered that the professor was dead, a series of subtle performances. . .
But I don’t know what is the use of scientists to study these? Confused. I just didn't see the director's intention

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