Psychophysics is the scientific study of the relation between stimulus and
sensation, and therefore the problems of psychophysics constitute some of the
most fundamental problems of modern psychology. For centuries thinkers have
recognized the importance of understanding sensation. In fact, experimental
psychology developed as an independent science largely because of the recog-
nition that the scientific study of sensation could yield insight into the workings
of the human mind.

Experimental psychology was established as an independent science when,
in Leipzig, 1879, Wilhelm Wundt founded the first laboratory for experimental
work exclusively directed toward understanding psychological processes. The
work of Wundt and other early experimental psychologists evolved from the
British empiricist and associationist schools of philosophy, which had firmly
established the idea of the senses as the key to human understanding. This idea
was reinforced by advances in sensory physiology, which suggested that the
problem might yield to scientific investigation.

But perhaps the single most important historical antecedent of experimental
psychology was psychophysics. Thus, for some psychologists the most signifi-
cant date in psychology is not 1879, the founding date of Wundt's laboratory,
but 1860, the date of the publication of Fechner Elements of Psychophysics.
Fechner's work, in providing methods and theory for the measurement of
sensation, gave psychology basic tools for the study of mind.

Today psychophysics remains a central part of experimental psychology.
Important recent changes in psychophysics are the development of the theory
of signal detection and the refinements of methods for directly scaling sensory
magnitude. These two advances have greatly broadened the applicability of
psychophysics to areas far beyond the original problems of measuring sensory
thresholds. Modern psychophysics can be credited with contributions to the
solution of problems in such diverse realms as sensory processes, memory,
learning, social behavior, and esthetics.

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