Indeed, the data recorded for a certain emotional expression in a naturalistic database will be different from one another.
although being adequate for recognition and classification tasks (if the data quantity is enough with respect to the task) this kind of data would most probably not be suitable to create parametric models such as Hidden Markov Models (HMM) (Rabiner and Juang, 1986) or Deep Neural Networks (DNN) (Hinton and Osindero, 2006;Anderson, 1995) with the goal of generating descriptors.