ABSTRACT
Gustav Fechner (1801-1887) argued for psychophysical parallelism, according to which the mental and physical worlds run parallel to each other but do not interact. Fechner developed the Weber-Fechner law, according to which the perceived intensity of a stimulus increases arithmetically as a constant multiple of the physical intensity of the stimulus or In other words, changes of physical intensity gallop along at a brisk pace while the corresponding changes of perceived intensity creep along. The Weber and the Weber-Fechner laws were the first laws to provide a mathematical statement of the relationship between the mind and the body. Also, Gustav T. Fechner introduced three psychological methods that were very important in establishing psychology as an independent, laboratorybased science, variations of which are still used today. Another significant contribution to the psychophysical foundations of psychology was made almost 100 years later when S. S. Stevens (1906-1973) demonstrated that psychological intensity (experiences of physical magnitudes) grows as an exponential function of physical stimulus intensity, that is, equal stimulus ratios always produce equal sensory ratios although different ratios hold for different sensory modalities
Wilhelm Wundt (1832-1920) used Weber and Fechner’s work on the relationship between subjective and physical intensities as a key component in the establishment of psychology as an independent science. Voluntarism, as Wundt’s new psychology became known, focused upon the specific subject matter of immediate conscious experiences of an adult studied by systematic introspection. According to Wundt, our immediate conscious experience is composed of sensations that have reference to some “external things” (stimuli) and affect or feelings (experiences more general than sensations that accompany intense sensations and fall on continua of pleasant to unpleasant, relaxed to strained, and calm to excited). Ideas arise from combinations of sensations derived from memory or previous associations of sensations. The active combination of these components of consciousness was referred to as apperception in Wundt’s laboratory. This mental process, apperception, allowed individuals to yield complex, unified conscious experiences as opposed to merely a conscious array of unorganized elements. The use of systematic introspection or the more specific strategy known as internal perception, a narrow focus on verbal immediate responses to precisely controlled stimuli by trained observers, was an attempt to avoid committing the stimulus error. The stimulus error arises when the person focuses primarily upon a description of the stimulus instead of the conscious experience evoked by a stimulus.
