Experiment 2

Task:

This task introduced an intertrial peroid in which the rat was in the dark. When the light went on the next bar pressed the light went off and their was %80 chance that a reward would drop.The intertrial lasted for 100 seconds

The idea here is that bar press duration should increase on nonrewarding trails. This is because the omission of the reward should generate the frustration effect leading to increased bar press duration.

Figure 3

Unfortunately the data failed to reflect much increase in bar press duration. The authors reject the idea that the frustration effect was the cause of response variation.

Analyzing the data from experiment 1 again :

Figure 5

The chart shows that as the likelihood that the a reward will be omitted the more bar press duration varies.

This leads the Authors to propose that in fact response variation is being controlled by the reduced anticipation of reward. They give 3 reasons to believe this.

1. Helps explain why the extend bar press duration last through to the end of the trial

2. It makes sense that response variation occurs when their reduced expectaton that response will bring about a reward.

3. The novelty of the effect was comensurate with the strength of the effect. (Unclear what this means)

Experiment 2 also seemed to contribute to the hypothesis.

1. Trials paid better than intertrials. Since anticpation of reward controls variation it makes sense that bar press duration varied more during intertrial then trial.

2. In trials where no reward is given more the subsquent intertrial peroid shows onger response duration. This makes sense because the trial sets the stage for the rat to believe that his response is irrelevant to acquire a reward.

3. Acquiring a reward during the trial would generate the anticipation that during other trials reward was more likely but should have no effect on the intertrial period bar press duration. The data demonstrated this.

Conclusion:

The first two experiment seems to show that resposne variation is controlled by reduced anticipation of reward.