PSY BEH 11A Lecture Notes - Lecture 19: Gustav Fechner, Power Law, Psychophysics
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Measuring the relation between a physical stimulus and the psychological experience. Hypothetical stages in the transformation of an external stimulus into an internal representation. Minimum intensity necessary to detect a stimulus. Also referred to as an absolute limen. Minimum intensity needed to detect a change in a stimulus. Also referred to as a difference limen or a just noticeable difference (jnd) I the intensity of a standard stimulus (e. g. brightness, loudness, pressure, etc. ) I + i the intensity of a stimulus that is just noticeably different than the standard. I / i = c: weber fraction. Psychological scale: equivalents steps in magnitude of sensation (jnd is constant, s1 = absolute threshold, s1 + jnd = s2, s2 + jnd = s3, s3 s2 = j(cid:374)d = . Fe(cid:272)hner"s la(cid:449: gustav fechner (1801 1887), father of psychophysics, s = k * log(i, sensation :: intensity. As x increases, y increases as well: problems. Physical systems have some sort of limit.