A Generic Knowledge as Probabilities

We adapt the generic knowledge from existing studies that are applicable to different datasets. Generic knowledge is expressed as probabilities. The generic knowledge is categorized into three types: expression-dependent single AU probabilities, expression-dependent joint AU probabilities, and expression-independent joint AU probabilities. 1) For expression-dependent single AU probabilities, two sources are considered. According to FACS, given an expression, AUs can be grouped into primary (P) and secondary (S) categories. The primary AUs are the most expressive AUs with respective to the expression, and the secondary AUs may co-occur with primary AUs providing additional supports for the expression.