n 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:

A. a comparison of absolute thresholds.
B. adaptation.
C. Weber's law.
D. stimulus generalization.

Weber's law

Agree.

The instructor is demonstrating Weber's law.

To understand why, let's first explain what Weber's law is. Weber's law is a principle in psychophysics that states that the just noticeable difference (JND) between two stimuli is proportional to the magnitude of the original stimulus. In simpler terms, it means that the increase or change in a stimulus needed to perceive a difference is not a fixed amount, but rather a relative amount.

In the given experiment, the students were first asked to add paper clips to their left hand until they were certain that the clips in the left hand weighed more than the ones in the right hand. The class average was seven paper clips before a difference in weight was observed. Then, they were asked to do the same procedure with psychology textbooks.

The key point here is that the students kept adding paper clips until they subjectively felt a difference in weight. This subjective perception of a difference in weight is similar to the concept of the just noticeable difference (JND) in Weber's law.

By increasing the number of paper clips in the left hand until the students felt a difference in weight, the instructor is demonstrating how Weber's law applies to their perception. According to Weber's law, the increase in the number of paper clips needed to perceive a difference in weight is proportional to the initial number of paper clips.

Therefore, the correct answer is C. Weber's law.