Yeah, this effectively becomes an "are you like me?" cultural test, which is just overflowing with implicit bias.

It's a "heads I win, tails you lose" test.

Yes, as a natural nervous laugher myself I had to course-correct later in life and learn to have gravitas. It is never beneficial to laugh, even if your counter-part is emotionally intelligent enough to know that it's nervous laughter because:

1) Your counter-part may not be emotionally intelligent enough

2) Deep-down, even if you know someone is showing you a nervous laugh it takes yet another level of emotional discipline to not be annoyed by it (like parents telling their kids "it's not funny".)

I can't stress enough how much extra trouble I got myself into by being a nervous laugher and no one telling me any better. As a child when you nervous laugh, the typical response from an adult is typically ~ "Oh yeah, let me double down and show you how not funny this situation is" which implicitly is trying to be a punitive lesson in life to change your behavior.

All this to say, this kind of police training/question is just cops making up pseudo-science and, as someone else pointed out, "heads I win, tails you lose" situation.

I'm immediately guilty in a lot of situations because I have some kind of automatic laugh when it's a high pressure scenario. I'm telling the truth but the laugh makes them think I'm lying, which then just cranks the pressure up higher as I have to convince them I'm not.

> I thought laughter was a sign of nervousness?

The cop in front of you decides what's nervousness or not.

No reaction ? Straight to jail

Nervous ? Straight to jail

Laughing ? Straight to jail

Laughing nervously ? Guess what, straight to jail

I don't think it's the worst heuristic of all time, especially just for the individual's awareness of the situation, but it shouldn't be legal grounding for anything