If you’ve noticed someone <lie> vs<lying> to you

[Tony_M]

Hello.

A: Are you good at spotting liars?
B: Probably, yes, but I never know how to expose lies the way that can stop liars from lying more.
A: If you’ve noticed someone lie to you, just shout at the top of your lungs, “Liar, liar, pans on fire.” I’m sure it’ll work.

Should I use the bare infinitive or the present participle in this context?

Thank you.

 

[emsr2d2]

A: Are you good at spotting liars?
B: Probably, yes, I'm quite good [at it] but I never don't know how to expose lies liars the in a way that can might/would stop liars from lying more them lying.
A: If you’ve noticed someone has lied to you, just shout at the top of your lungs, “Liar, liar, pants on fire.” I’m sure it’ll work.

Should I use the bare infinitive or the present participle in this context?

See above. As you can see, I wouldn't use the bare infinitive or the present participle having started with the present perfect (If you've noticed). Here are the versions I might use:

If you notice someone lying to you, just shout ...
If you notice that someone is lying to you, just shout ...

I'd open with the present tense because you're talking about what you suggest becomes a general habit.

 

[tedmc]

I think the present participle is more common and natural.

 

[Tarheel]

"You're lying" is common enough. "You're a liar" is also used.

 

[jutfrank]

There doesn't seem to me to be a reason for retrospection here at all. When giving advice to people as with the context here, it's typical to keep everything simple and to look forward rather than back. If you don't need any aspect, don't bother with it:

If you (ever) notice someone lie to you ...

If you want to suggest that the lying is ongoing and unfinished, as opposed to a single complete event, then the -ing form will do that:

If you (ever) notice someone lying to you ...

But understand that these are essentially two different meanings.