A class that includes within it other classes that can themselves function as operant classes, as when generalized imitation includes all the component imitations that could be separately reinforced. Higher-order classes may be a source of novel behavior (e.g., as in the generalized indication of behavior that the imitator had not seen before). They also have the property that contingencies may operate differently on the higher-order class than on the classes that are its components. For example, if all instances are reinforced except imitations within one component class (e.g., jumping whenever the model jumps), that class may change with the higher order class rather than with the contingencies arranged for it (i.e., imitations of jumping may not extinguish, even though no longer reinforced)- Control by the contingencies arranged for the higher-order class rather than for component classes defines these classes; the component classes are sometimes said to be insensitive to the contingencies arranged for them. A higher-order class is sometimes called a generalized class, in that contingencies arranged for some component classes within it generalize to all the others. Generalized matching and rule governed behavior are examples of higher order classes.