1. A method, implemented by a computing system comprising one or more processors, the method comprising: receiving, using one or more of the processors, a first natural language input; measuring, using one or more of the processors, characteristics of the first natural language input; using the characteristics to train, using one or more of the processors, a first classifier for comparing the characteristics of the first natural language input with indicators of non-native usage; gathering additional natural language input; using the first classifier on the additional natural language input for indicating a portion of the additional natural language input as having non-native usage; combining the additional natural language input indicated as having non-native usage with the first natural language input, into a combined natural language input; measuring the characteristics of the combined natural language input; and using the characteristics of the combined natural language input to re-train the classifier, to create a refined classifier for indicating non-native usage of the language.