After establishing that mental and physical events varied systematically, and thus showing that a science of the mind is indeed possible (contrary to the beliefs of such individu- als as Galileo, Comte, and Kant), Fechner employed several methods to further explore the mind–body relationship:
■ The method of limits (also called the method of just noticeable differences): With this method, one stimulus is varied and is compared to a stan- dard. To begin with, the variable stimulus can be equal to the standard and then varied, or it can be much stronger or weaker than the standard. The goal here is to determine the range of stimuli that the subject considers to be equal to the standard.
■ The method of constant stimuli (also called the method of right and wrong cases): Here, pairs of stimuli are presented to the subject. One mem- ber of the pair is the standard and remains the same, and the other varies in magnitude from one presentation to another. The subject reports whether the variable stimulus appears greater than, less than, or equal to the standard.
■ The method of adjustment (also called the method of average error): Here, the subject has control over the variable stimulus and is instructed to adjust its magnitude so that the stimulus appears equal to the standard stimulus. After the adjustment, the average difference between the variable stimulus and the standard stimulus is measured.