Answer:
fixed-interval
Step-by-step explanation:
Fixed-interval schedule: The term fixed-interval schedule is used in the operant conditioning technique. It is defined as the schedule of reinforcement in which the very first response to a stimulus is being rewarded after a particular time has been passed and it affects the behavior.
The fixed-interval schedule in operant conditioning, the interval time between two responses will be the same always.
In the question above, Colin's behavior is reinforced on a fixed-interval schedule.