Final answer:
The variable ratio reinforcement schedule leads to the highest rate of responding in the shortest period of time.
Step-by-step explanation:
In operant conditioning, the variable ratio schedule leads to the highest rate of responding in the shortest period of time. This schedule is unpredictable and produces a high and steady response rate, with little to no pause after reinforcement. An example of the variable ratio reinforcement schedule is a slot machine at a casino that rewards gamblers with money based on varying amounts of responses.