What causes some people to automatically assume they're being lied to?

I think that if it wasn’t for my influence my husband would be a moderate conspiracy theorist…maybe worse! He was scheduled to fly out of town today. He just came down and said he might not be going. He said, the flight into Dallas was cancelled.
I said, “Must be the weather.”
He said, “Supposedly. That’s what they’re saying anyway. I don’t think the weather’s that bad there.”
I’m all, “Well, perhaps terrorists have taken over the airport?”

I mean, what is there to doubt in the explanation? What other reason would they have for shutting down an airport and losing millions of dollars a day?

What causes people to be so automatically suspicious? Do you think they were lied to a lot as a kid or something?