Randi gives people horoscopes supposedly made by professionals based on their date and place of birth. He has the people rate the accuracy, and scores pretty high. Then he tells them that they all got the same horoscope!
Derren Brown did the same trick.
What can we learn about people from this? One thing is that they have certain sorts of broad similarities. If you talk about those areas, pretty much anyone can relate to what you say. Those areas include having a family, a love life, relatives, feeling misunderstood, and having insecurities. Those are just some obvious ones. I'm not an expert and I haven't even thought about it much. I'm sure there are others. You could learn them just by reading some horoscopes.
Despite everyone having similarities, horoscopes don't work perfectly. Another thing going on is that people focus in on the parts that seem right and ignore the ones that seem wrong. They help it to work.
That's what they do if they are friendly or sympathetic, at least. Other times people can be hostile to something and focus on the parts they disagree with. That often happens in arguments between people who strongly disagree. Sadly, it does an effective job of preventing people from learning from each other.