I thought a lot about this things, I red books and studied myself and familymembers, talked about this and it was pretty obvious that it is true. And I mean if diffrente cultures around the world sepperated from each others developed nearly equal systems (other starsigns but as good as equal characteristics), that can not be accidental. Maybe in 50 years the quantum physics can say more about this. And even Shakespeare said: "there are things between the sky and earth than school wisdom will let you imagine."
To prove that Zodiac signs affect personality, there has to irrefutable proof that a relationship exists between the signs and personalities. The proof must be quantifiable and scientifically conducted. There are no science based studies to proof such a relationships exists. Therefore, since there is a lack of proof and studies, it can be determined that Zodiac signs do not affect personality. If one plans to refute my answer, please submit proof of a scientific, double blind study that shows such a relationship exists. I will warn you in advance however, that no such proof exists.