Final answer:
The principle upon which behavior modification depends is operant conditioning, which is a form of learning in which behavior is strengthened or weakened by its consequences.
Step-by-step explanation:
The principle upon which behavior modification depends is operant conditioning, which was proposed by psychologist B.F. Skinner. Operant conditioning is a form of learning in which behavior is strengthened or weakened by the consequences that follow it. According to this principle, behaviors that are followed by positive reinforcement are more likely to be repeated, while behaviors followed by punishment are less likely to be repeated.