Do guys always get an when they are attracted to a woman?

Is that their sign that they're attracted to her, or is it ever that a guy can see a girl and think she's beautiful or "hot" and just like her but not ever get the body reaction? I'm asking because I went to a job interview tonight and the interviewer seemed to really like me and it was awkward. He told me I was making him nervous too, and was flustered with his words and I guess I'm a pervert but I started wondering if he was getting like... you know,.. like w/e, down there. :/