CRFs are a type of discriminative undirected probabilistic graphical model. Generative training algorithms are often simpler and more computationally efficient than discriminative training algorithms. Negative emotion stimuli will serve as negative discriminative stimuli, disincentives. Statistical algorithms can further be categorized as generative or discriminative. So, emotion stimuli also have reinforcing value and discriminative stimulus value. Some stimuli that is considered discriminative are signals, targets and cues. They can be generative and discriminative models. Application-specific details ultimately dictate the suitability of selecting a discriminative versus generative model. The "generative" network generates candidates while the "discriminative" network evaluates them. Various discriminative algorithms can then tune these weights. That is, a discriminative stimulus is also a "conditioned reinforcer". Racially discriminative and segregationist principles were not novelties in South Africa. A variant of the previously described discriminative model is the linear-chain conditional random field. The antecedent stimulus is called a discriminative stimulus (S). In purely discriminative tasks, DSNs outperform conventional DBNs.