Email and text messages have a ‘body language’ all their own, reports Elizabeth Bernstein in The Wall Street Journal (5/20/14). It’s relatively easy to ‘read’ someone face-to-face, but a bit trickier when the only clues are of a digital sort. One tip-off is the "use of emphatic language. It doesn’t necessarily mean s/he is lying, but rather that s/he really wants you to believe what is being said. This is also the case when a person keeps saying the same thing over and over in slightly different ways."
In person, "someone may unconsciously distance himself by crossing his arms in front of him. In writing, he can achieve this same effect by omitting personal pronouns and references to himself from a story. Say he receives a text that says, ‘Hey, I had a great time last night, did you?’ He might reply, ‘Last night was fun.’" Then there’s the "unanswered question," which could mean s/he "doesn’t like saying no, or doesn’t want to hurt your feelings," or that s/he is "keeping something from you."
"This is all very subtle," says Tyler Cohen Wood, author of Catching the Catfishers. Pay attention if a "usually chatty" person turns quiet, or someone who generally provides a lot of details suddenly goes vague on you. Phrases like "pretty sure" and "must have" signal evasion, and "to be honest" can mean just the opposite. Watch out for "tense hopping." If someone is telling a story, and switches from past to present tense, it just might mean s/he’s making something up on the fly.