Have you seen this thought bubble?

At first glance it looked like when a sim with a Loner trait gets anxious about being around others too long, but the loner anxiety has tan coloured sim-figures in the picture. It also looks a little bit like the wish to meet someone or change relationship with the sim finder or relationship transmogrifier, which are abilities gained with the skill of Social Networking, available on the sim's phone. I don't know what the other Social Networking abilities are, but it is probably one of those.