A BCBA is wоrking with а child in а schооl setting who engаges in aggression towards the classroom teacher and other adults multiple times throughout the day. The BCBA recommends an intervention where the teacher sets 10-min intervals and provides reinforcement in the form of delivering a token at the end of each 10-min interval as long as the child does not engage in aggression during that interval. If the child engages in aggression during that interval, the teacher resets the interval. This is an example of: