"Psychophysics is commonly defined as the quantitative branch of the study of perception, examining the relations between observed stimuli and responses and the reasons for those relations. This is, however, a very narrow view of the influence it has had on much of psychology. Since its inception, psychophysics has been based on the assumption that the human perceptual system is a measureing instrument yielding results (experiences, judgments, responses) that may be systematically analyzed. Because of its long history (over 140 years), its experimental methods, data analyses, and models of underlying perceptual and cognitive processes have reached a high level of refinement. For this reason, many techniques originally developed in psychophysics have been used to unravel problems in learning, memory, attitude measurement, and social psychology. In addition, scaling and measurement theory have adapted these methods and models to analyze decision making in contexts entirely divorced from perception."

'Psychophysical Methods' by Walter Ehrenstein and Addie Ehrenstein gives a description of Fechner’s techniques and details those extensions and modifications of psychophysical methods that may be helpful to the modern neuroscientist (opens in PDF format).