Answer: 3. variable ratio
Options:
1. fixed interval
2. fixed ratio
3. variable ratio
4. variable interval
Explanation: The variable ratio of reinforcement uses rewards to create a high and steady rate of response. The rate of reward for a target behavior is unpredictable so the rat does not know when its response will get a reward. It will keep responding until the reward is delivered.
The options listed above are schedules of reinforcement. They are schedules used in rewarding target behavior in Operant conditioning.
