Final answer:
The description illustrates the just-noticeable difference (JND), which refers to the smallest detectable difference in a stimulus that can be perceived 50% of the time. Detecting the difference between weights is proportional to the magnitude of the stimulus, making it easier to detect the difference between lighter objects and more challenging with heavier ones.
Step-by-step explanation:
The student's description illustrates the concept of just-noticeable difference (JND), which is an essential concept in the field of psychology, particularly in sensory perception studies. According to the Weber-Fechner law, the JND is the minimum level of stimulation that a person can detect 50% of the time, and it is proportional to the magnitude of the stimulus. In other words, the likelihood of detecting a change in weight depends on the initial weight; therefore, a difference between 1 and 2 units of weight (doubling the weight) is more easily detectable than a difference between 20 and 21 units of weight (a mere 5% increase).
Applying this to the examples given, it's easier to notice the difference between a one-pound bag of rice and a two-pound bag because the weight has doubled. However, when comparing heavier items, such as a 20-pound bag of rice to a 20.5 or 21-pound bag, the weight difference represents a smaller percentage change, making it less detectable.
The concept of JND is important to consider in various practical scenarios, such as mailing packages, because it helps understand how humans perceive differences in weight and why even small variations in weight can impact shipping costs.