The fact that Mason runs because it reduces his stress levels means that the running is maintained by a negative reinforcer.
This refers to anything that encourages us to do something to act against it because it has a negative effect on us.
Stress has a negative effect on humans and so Mason is trying to get rid of it by running which makes stress a negative reinforcer.
Find out more on negative reinforcers at https://brainly.com/question/15103927.
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