Psychophysics studies the relationship between physical stimuli and subjective perceptions. Experiments use objectively measurable stimuli to determine thresholds and perceptible differences, and can take various forms, including ladder procedures.
Psychophysics is a subfield of psychology that addresses the relationship between physical stimuli and subjective responses, or perceptions. The term “psychophysics” was coined by the field’s founder, Gustav Theodor Fechner, in 1860. Earlier scientists, including the German physiologist Ernst Heinrich Weber and the medieval scientist Alhazen, conducted similar experiments, although the field was not clearly defined until Fechner’s work. Experiments can focus on any sensory system: hearing, taste, touch, smell or sight.
Objectively measurable stimuli are used in psychophysics experiments, such as lights that vary in brightness or sounds that vary in volume. A threshold, or limin, is the point at which a subject can detect a stimulus or a change in the stimulus. Stimuli that fall below the threshold are considered subliminal or undetectable.
An absolute threshold, or detection threshold, is the point at which a subject can detect the presence of a stimulus, while a difference threshold is the magnitude of the perceptible difference between two stimuli. For example, a difference threshold can be tested by asking a subject to adjust one sound until it equals another and then measuring the difference between the two sounds. The point of subjective equality (PSE) is the point at which the subject considers two stimuli to be the same, while the just perceptible difference (JND) or limen difference (DL) is a difference between stimuli perceived 50% of the time.
Experiments in classical psychophysics can take many forms. They may use the ascending limit method, in which stimuli are presented starting at a very low, undetectable level, then gradually ramped up to notice the point at which they become perceptible. Another method is the constant stimulus method, where the stimuli are administered in a random order rather than in ascending order. The regulation method requires the subject to manipulate stimuli until they are barely perceptible against a background, or until they are the same as or just different from another stimulus.
Newer methods in psychophysical experimentation include those called ladder procedures, first used by Hungarian biophysicist Georg von Békésy in 1960. In experiments using ladder procedures, stimuli are first presented at a high level and detectable. The intensity is decreased until the subject makes a mistake in perceiving it. After the error, the scale is reversed, increasing in intensity until the subject responds correctly. At that point, the intensity is reduced again. The values for the reversals are then averaged. The ladder method helps experimenters narrow down to the threshold.
Protect your devices with Threat Protection by NordVPN
