Summarize the following:
"Baseline" behavior means how they normally behave, when they aren't under stress. Knowing a person's baseline behavior is important, because you can compare their current behavior to their baseline to see if something is off.  Different cultures have different norms with regards to eye contact. Western cultures usually consider it a sign of respect and engagement, while some Eastern cultures consider it rude. Certain disabilities, like ADHD and autism, can involve unusual baseline behavior. For example, perhaps your autistic friend usually fidgets and avoids eye contact. You ask her where she was last night, and she plays with her hair, looks at your feet, and says she was watching movies at home. Even though this behavior might signal lying in non-autistic people, it's normal for her, so you can assume she's telling the truth. This means that there's a lot of overlap between signs of lying and signs of stress.  Be cautious about jumping to the conclusion that someone is lying when they look stressed. It's possible that something else is bothering them. When speaking with someone and you ask them about how their day has been, they usually will reply “Oh, it was fine. How was yours?”  You won't see a lot of eye signals from this; these are almost programmed responses. It can be hurtful to accuse someone else of lying, especially if it turns out that they were telling the truth. Avoid jumping to conclusions, or harming their reputation without very good cause.
Think about the person's baseline behavior. Recognize that people usually feel uncomfortable when they lie. Know that basic questions are unlikely to elicit eye signals. Be careful about what you do.