Lightbulbs and plus signs??

You might get a better answer out of the Sims 4 section. This is the Sims 3 side of the forums.

Are you playing TS4? I only ask this given your posting history is in the Sims 4 forum and you're asking this question in the Sims 3 General Discussion forums... ;)

Oops! Wrong section!

Check if there an traits for the lot. I noticed mine do this when they are doing something connected to a lot trait. For example if you have the homey trait and your sim is cleaning then they get the little light bulbs and plus signs. It just means they are learning that skill faster.

Yup, those are caused by lot traits. There are two ways to turn them off, you either remove the lot traits (and thus the benefits they give) or use a mod to remove the fx (which is what I do, because I want lot traits, I just don't want them to mess up my screenshots). Unless there's a cheat that turns them off, but I haven't heard of it.