Reverse psychology is about the only psychology that works on gamers. Sometimes.

If they're too genre-savvy you may need to go for reverse-reverse psychology. Where you say what you want them to do, so they think you're trying to trick them into not doing that, so they go ahead and do it.

Of course this leads to doubly genre-savvy gamers not falling for anything less than reverse-reverse-reverse psychology. Where you say you want them to do what you don't want them to do, so they think you're deliberately saying what you do want them to do so that they'll think you don't want them to do that in order to trick them into going ahead and doing that, only then they're too smart for that and decide not to do it!

Which leads to reverse-reverse-reverse-reverse psychology. Where... you get the idea.

Make sure to make maximum use of these principles when designing dungeon traps that the PCs either should or should not touch...

Transcript

R2-D2: Let me rewind that a bit.
[SFX]: < bop bapip >
Leia: You and 3PO need to get these plans to Senator Binks on Naboo.
C-3PO: There you go, our mission.
Adam: Not gonna happen. Your Rebellion will have to wait until I complete my quest.
R2-D2: Hmmm. Fair enough. But as my new owner, I must ask one boon of you.
[SFX]: < bippity squee buzz bedoop doop whir eemoo ping >
R2-D2: See this thing attached to my chassis? When you're cleaning me, please don't take it off me.
[SFX]: < doop buzz prow squee beedle kibuzz boop kibuzz prow >
Adam: Why? What happens if it's removed?
R2-D2: I don't even want to think about it. Truly.
[SFX]: < doop boop pating >
Adam: Really?
R2-D2: I'm serious. I really don't want you to remove it. Please.
[SFX]: < oowoo boop kibuzz >
Adam: Hmmm.
R2-D2: You'd be doing me a favour.
[SFX]: < squee eeyoo >
{beat}
Adam: I take it. What happens?
GM: Pete just earned 50 XP.