5.05 - Interval Schedules

Overview of Reinforcement Schedules

• Reinforcement schedules can be categorized into two types: response-based and time-based schedules.

Fixed Interval Schedule (FI Schedule)

• Definition: A fixed interval schedule provides reinforcement after the first response following a predetermined time interval.

• Example: An FI-3 minutes schedule.

  • A timer starts, and after 3 minutes, the first response is reinforced.

  • Responses before the time elapses do not yield reinforcement.

• Key Features:

  • Only the first response after the set interval is reinforced, not multiple responses.

  • Encourages waiting until the end of the interval to reinforce behavior.

Scallop Effect

• Observation: The pattern of responding in a fixed interval schedule results in a scalloped response curve.

• Characteristics:

  • Initially low response rate at the beginning of the interval.

  • As the end of the interval approaches, the response rate accelerates sharply.

  • Results in a distinctive graphical shape resembling a scallop.

• Real-World Example: Checking the time or behavior while waiting for a predictable bus arrival:

  • Low checking frequency after missing the bus in the first few minutes.

  • Increased checking frequency as the expected arrival time nears.

• Contingency Note: The example of checking the watch does not perfectly exemplify fixed interval scheduling, as it lacks a direct contingency to the bus's arrival.

Variable Interval Schedule (VI Schedule)

• Definition: In a variable interval schedule, reinforcement is delivered after the first response that follows a variable length of time.

• Example: A VI-30 seconds schedule.

  • Averages to reinforce a response approximately every 30 seconds, but the actual time varies (e.g., sometimes it's 2 seconds or 60 seconds).

• Main Effect: Similar to fixed interval, one response after a varying period of time results in reinforcement.

Response Characteristics of VI Schedule

• Response Rate: The response rate is low and constant,

  • Not displaying the scallop pattern as seen in fixed schedules.

  • Similar to the consistent response rate observed in variable ratio schedules, but generally flatter.

• Example of Application: Pop quizzes in education.

  • Students may study at a consistent, moderate pace to prepare for potential quizzes that are unpredictable.

  • The schedule encourages studying regularly without knowing exactly when a quiz may occur.

Conclusion of Simple Reinforcement Schedules

• A summary of the four basic reinforcement schedules:

  • Fixed Ratio (FR)

  • Variable Ratio (VR)

  • Fixed Interval (FI)

  • Variable Interval (VI)

• Future topics will involve more complex reinforcement schedules.