It’s not they are definitely lying. It’s just that if their weren’t advancement opportunities, they would be still saying there were. That’s how it goes.
This is a common problem in human communication. Here’s how it often goes:
A: How do I look?
B: You look great!
A: Yeah, but if I looked bad, would you tell me?
The same thing applies to opportunities to advance. What company is going to answer your question by saying “no, there really aren’t opportunities to advance?”
© Flickr User Kenny Louie
But of course, you want to find out if you can move up in the company. So a better question to ask an interviewer is: “How did you get your start at this firm?”
Try to find out how they advanced through the ranks. Did they have a title change or a chance to work on more interesting stuff?
That’s a question they will answer honestly. And if they haven’t really ever moved up, it might be a sign that you won’t be able to either.