New students can come into class being sensitive to contact. What students go through in class, under proper supervision, is a systematic desensitizing. Students start with very little or very light contact. In their own time time they progress to more moderate contact and eventually beyond that. One of the practical effects of this progressive contact is that students can distinguish between a perceived threat and a threat that needs to be responded to in kind. Students ability to control their behavior towards a perceived threat grows as they progress. This keeps tempers in check and keeps situations from escalating to unnecessary levels. An added benefit is that, if necessary, the contact from an unexpected attack can be absorbed by students and then be responded to accordingly. This makes their ability to defend themselves more effective.