As a younger INFJ, I would get a feeling in the pit of my stomach sometimes when I was with other people, a feeling that’s hard to describe. I knew that it made me feel uneasy all of a sudden, but I didn’t know why.
As I matured and have become more self-aware, I learned to recognize that feeling as my INFJ Radar telling me that someone is lying. And it is extremely accurate.
I may not immediately know WHY that person is lying, although that too will usually readily become apparent, but I know they’re being deceptive in some way.
Whether I acknowledge that I know they’re lying, or whether I let them continue to think I’m falling for their bullshit, depends on the person and situation.
If I fail to realize someone is lying, it’s usually only because I’m distracted in some way.
If someone has my full attention, then it’s a bad idea to be dishonest, because I will know.