Sims yawning at each other?

[Crystallyne]

I've been playing Sims 3 for a long time, and one of my favorite things to do is explore tombs.  I usually take a single Sim alone, but my current Sim wanted to travel with his boyfriend, so I took them both to China.  My main Sim is doing most of the exploring and stuff in the tomb, but I have his boyfriend doing stuff like grabbing treasure, checking for and disarming traps, that kind of thing.  This is the first time I've ever taken 2 sims into a tomb, and I'm noticing something strange...

They keep yawning at each other!

Like they literally will yawn as they walk by each other, or glance in the other Sim's direction.  All their motives are filled, their relationship is maxed, and I had them take a break to talk for awhile just to see if that helped...  But they immediately resumed yawning at each other!  It doesn't matter if I give them both something to do or not, they'll yawn at each other on their way to do whatever task I gave them!

I'm not really irritated by it, more half-amused.  But it is getting really old, really fast!

Has anyone else ever encountered this behavior before?  I don't know if it makes a difference, but they're both teenagers, as well.  I can't see this be some weird quirk caused by a mod, though I have plenty of those.  It's just...weird!  LOL

[Junan]

 Could they both have the Light Sleeper trait? That causes them to yawn more often than normal.

[Crystallyne]

Nope, neither had the light sleeper trait.  That's interesting to know, though.

I've noticed it a few other times as well, since then.  I have no idea what is causing it.  In other cases, it was other Sims yawning at each other.  And I do mean yawning AT each other.  I had a party at my Sim's house, and one of my Sims and one of the guests started yawning whenever they got near each other, clearly looking at each other as they did so.  They also (usually) follow it with this kind of dismissive gesture of their hands, and usually have the portrait of the other person in a thought bubble when they're doing this whole interaction.

I know Sims will yawn if a party is boring, but it was something very different from that.  They also left the party with some form of "I had a blast!" message, so they weren't bored with the party itself.

It's almost like at some point two sims get locked into some weird thing with each other that they will yawn AT each other whenever they come near.  It persists as long as they remain on the lot, or perhaps as long as they're in each other's vicinity for awhile.  It's like they're bored of seeing the other person, or bored with each other.

It's just really odd behavior that I've never noticed before!