Hear me out: if someone believes in horoscopes, they know what each sign mean. Which means they recognise themselves into a sign. Which means they will mostly act in ways to conform to that sign, giving you a way to figure that person out. The sign tells it all, it’s a self-fulfilling prophecy.
Cool idea, but I spent a lot of time amongst people who believed in star signs when I was young.
They will say “Virgo: the most generous star sign, OMG that’s so me. I like, super generous”, despite the fact they have never given a cent in charity in their life.
None of it influenced their behaviour apart from the ‘lucky numbers’, which probably got them buying a few more lotto tickets.