Well, there are if you begin to stereotype people in association with the what seem arbitrary behaoviours they engage in. Then patterns start to show up. The key element of a pattern is that the pattern becomes predictable. That conventions are human made, and human acted on, means that there are as many exceptions to the convention as not. This makes the timing unpredictable - unlike sunspots.
Conventions then are something people are inculcated into knowing, or they are left out of knowing.
We judge each other strongly by the use or absense of key convetions. I have been trying to learn by pattern recogntion something that is learne donly by apprenticeship. Perhaps I will not be able to learn these things at all. Or perhaps I should relax and use them - I amy already know them.