How can you tell the difference between an interval and a ratio schedule of partial reinforcement?

In the context of operant conditioning, partial reinforcement refers to a situation in which a response is reinforced only some of the time. There are different types of partial reinforcement schedules, two of which are interval schedules and ratio schedules. Understanding the difference between these two can help in identifying the type of reinforcement schedule being used in a given scenario.

**Interval Schedules:**

An interval schedule is based on the passage of time. There are two main types of interval schedules:

1. Fixed Interval (FI) Schedule: A reinforcement is given for the first response made after a fixed amount of time has passed since the last reinforcement. For example, if a pigeon is on a 2-minute fixed interval schedule, it will receive food for the first peck at a response key after 2 minutes have elapsed since the last reinforcement.

2. Variable Interval (VI) Schedule: A reinforcement is given for the first response after a variable amount of time has passed. The interval length varies around a mean value. For instance, a pigeon on a variable interval schedule might receive food for the first peck after an average of 2 minutes, but the actual interval could range from 1 to 3 minutes between reinforcements.

**Ratio Schedules:**

A ratio schedule is based on the number of responses made. There are two main types of ratio schedules:

1. Fixed Ratio (FR) Schedule: A reinforcement is given after a fixed number of responses. For example, a rat might be reinforced every 10th lever press.

2. Variable Ratio (VR) Schedule: A reinforcement is given after a variable number of responses, with the number required varying around a mean. For example, a rat might be reinforced on average every 10th lever press, but the actual number required can vary from 1 to 20.

**Key Differences:**

- **Time vs. Response Count:** Interval schedules depend on the passage of time, whereas ratio schedules depend on the number of responses.

- **Predictability:** Fixed schedules (both interval and ratio) are predictable because the reinforcement criteria (time or number of responses) do not change. Variable schedules are unpredictable because the criteria for reinforcement vary.

- **Response Rate:** Ratio schedules tend to produce higher rates of responding than interval schedules because the reinforcement is directly contingent on the number of responses, not the passage of time.

- **Post-Reinforcement Pause:** Fixed interval schedules often result in a post-reinforcement pause (a period of no responding following reinforcement), which is less common in ratio schedules, especially variable ratio schedules.

In summary, to tell the difference between an interval and a ratio schedule of partial reinforcement, you need to observe whether the reinforcement is contingent on the passage of time (interval) or the number of responses (ratio), and whether the schedule is fixed or variable.