In a classroom experiment, students were asked to place one paper clip in each hand. They were then instructed to add paper clips to the left hand until they were certain that the clips in the left hand weighed more than the paper clips in the right hand. The class average was seven paper clips before a difference in weight was observed. Students were then asked to follow the same procedure with psychology text books. The instructor is demonstrating:

1. a comparison of absolute thresholds
2. Adaption
3. Weber's law.
4. stimulus generalization

weber's law

The instructor is demonstrating Weber's law.

Explanation:

Weber's law states that the just noticeable difference (JND) between two stimuli is a constant proportion of the original stimulus intensity. In simple terms, it means that the difference between two stimuli must reach a certain threshold before it can be perceived as different.

In the given scenario, the students were asked to add paper clips to one hand until they were certain that the weight in that hand was greater than the other hand. The fact that, on average, they added seven paper clips before perceiving a difference in weight indicates that there is a specific threshold (JND) that needs to be exceeded for them to notice the difference.

By repeating the same procedure with psychology textbooks, the instructor is demonstrating Weber's law because the stimulus (paper clips) was changed, but the concept of a threshold for detection remains the same. This experiment allows the students to experience and understand how Weber's law works and how it applies to different stimuli.

Therefore, the correct answer is option 3: Weber's law.