The Concept that Drew is applying is known as Stimulus control concept of behavior modification.
Basically, the behavior modification means a process of changing patterns of human behavior over the long period through using use of various techniques.
One of the techniques of behavior modification includes the Stimulus control technique because usually, some situations in which a behavior is triggered is by presence or absence of some stimulus, thus, the modification helps to alter the patterns.
Therefore, the action of Drew not to walk by the vending machines is known as applying Stimulus control concept of behavior modification.
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