Which type of stimulus change is a person least sensitive to according to Weber's constants?

The correct choice is based on Weber's Law, which describes how the perception of change in a stimulus is relative to the original intensity of that stimulus. Weber's constants indicate that humans are less sensitive to changes in certain stimuli as they get stronger.

In the case of the saltiness of food, it is generally established that our taste sensitivity to salt is lower compared to our sensitivity to changes in other stimulus categories, such as the heaviness of weights or the brightness of lights. For stimuli that are continuously consumed or experienced, like taste, the relative change needed for us to perceive a difference is larger than for sound pitches or weight heaviness. This means that our ability to notice small increases or decreases in saltiness is diminished, making us less sensitive to this type of stimulus change.

In contrast, other options like sounds, weights, and brightness typically demonstrate greater sensitivity to changes because these sensations are often governed by distinct adaptive thresholds, where our awareness to differences can be more easily detected. Thus, the insensitivity in detecting changes in the saltiness of food aligns with the understanding of Weber's constants.