On the first trial, the rat had to press the bar three times to get a pellet of food. on the second trial, seven bar presses were needed. although it continued to vary from trial to trial, on the average the rat was reinforced for every five bar presses. the rat is on a schedule of reinforcement.

Variable Ratio  Schedule

Explanation:

First, there are two different types of reinforcement:

The positive reinforcement applies a stimulus to increase the frequency of the desirable variable.

The negative reinforcement removes a stimulus to increase the frequency of the desirable variable.

However, the positive reinforcement divides itself in different types:

A continuous reinforcement schedule gives us a reinforcement every time we engaged in the desired conduct.

On the other side, the partial reinforcement schedule  also divides itself in

And these divide themselves in fixed or variable.

In the example, the rats get a pellet of food, so we're talking about a reinforcement. They don't get a reward EVERY TIME they press the bar so we are not talking about a continuous reinforcement but a partial reinforcement. Since the rats press the bar and get a reward after certain NUMBER of times, we're talking about a ratio schedule. Finally, the number of times they need to press the bar to get a reward VARIES from trial to trial so this is a Variable Ratio Schedule.

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