Psychophysics Flashcards
After earning his MD and serving as a physician in the Prussian army, he took a position as an associate professor of physiology at Königsberg, followed by positions at Bonn, Heidelberg and finally as the Chair of Physics at Berlin. (nota bene)
Herman Helmholtz
Discovered the speed of the nerve impulse bringing the mind to time. His theories of vision and hearing coupled with his tremendous influence in the physics of optics made him an exceptionally influential theorist and researcher in the area of sensation and perception, a field in its infancy in his lifetime.
Herman Helmholtz
Was a major influence in bringing Empiricism to Germany against the phenomenological/nativist perspective that characterized Germany
Herman Helmholtz
He broke with the German traditions of phenomenological introspection and nativism to espouse a radically empirical approach to human sensation in the British empiricist tradition.
Herman Helmholtz
He disagreed with the nativist position of Lotze (and Leibniz and Descartes!) on the phenomenon of depth perception.
Herman Helmholtz
While Fechner later provides the methods and the measurement system for psychophysics, he provided the knowledge of the sensory systems.
Herman Helmholtz
He agreed with Berkeley and the British empiricists that depth perception was learned.
He argued that depth perception is based on unconscious inferences which arise from the habitual experience of constancy.
Herman Helmholtz
Accordingly, “lightning fast” geometric calculations (see Descartes) are not necessary.
Note that retinal disparity produces two images but we cannot consciously unblend them. Thus, the blending of the images is irresistible and unconscious. (Remember the hole in the hand illusion here)
Sets up the distinction between sensation (a-priori) and perception (a-posteriori).
Herman Helmholtz
Represented a strong and influential push in the direction of pure empiricism which set the stage for Wundt, Fechner and Ebbinghaus, whose empiricist approaches may not have taken hold without Helmholtz establishment of the empiricist zeitgeist. Wundt was his assistant for several years (nota bene).
Remember that empiricism and its passive mind approach opened the door for an experimental study of the mind/machine using physiology.
Herman Helmholtz
After his early research on vision and audition, he moved to the cutaneous and muscle senses.
Using hog bristles set at differing distances in wood holders, he asked blindfolded subjects to tell him if they felt one or two points.
This research led to the first demonstrations of sensory thresholds in a controlled laboratory setting.
Ernst Weber
He proceeded to map the surface of the body for two point limens (thresholds) and found the separation of points necessary to detect a difference varied systematically on various regions of the body.
His theory that the points had to fall across two sensory circles (next slide), is only of historical significance.
Ernst Weber
His second major contribution was the discovery of the just noticeable difference (j.n.d.).
For weight judgment the j.n.d. is 40:1. That is to tell that a second weight is heavier it must be 1/40th heavier (e.g.. 40 to 41, 80 to 82, 120 to 123 etc.).
Ernst Weber
The conclusion was that difference limens are relative rather than absolute.
While the ratio was different for each sense, it was a constant within the sense.
Therefore, there is not a 1:1 correspondence between physical and sensory reality.
Ernst Weber
Since he was concerned with physiology and not psychology, he never pursued the implications of his findings for the measurement of the mind or accuracy of perception.
His research was well designed and well controlled.
The j.n.d. and his use of difference thresholds set the stage for Fechner’s work.
Ernst Weber
As a humanist, he attacked the medical establishments materialism, lampooning them in satirical essays.
Gustav Fechner
A recurrent theme in his writings was that the universe should be viewed from the perspective of conscious experience (the day view) rather than inert matter (night view).
Gustav Fechner
Changed from medical studies to math/physics, translating the Handbook of Chemistry and Physics from French to German ( through 12 editions)
Gustav Fechner
Developed an interest in the physics and physiology of vision. (note the compatibility with the zeitgeist)
By his 30s, he had destroyed his vision by looking at the sun through colored glasses to study afterimages (Note his use of inductive phenomonology).
Gustav Fechner
The combination of overwork and despondence over his visual problems, neurotic depression, hypochondria and suicidal ideation, led to his resignation from the Chair of Physics in 1840, and medical retirement in 1844.
He continued to contribute to in major ways to the development of psychophysics from 1844 through 1888.
Gustav Fechner
His illness turned him toward philosophy and he became obsessed with resolving the mind body problem scientifically. As a double aspectist, he was determined to show the mind and body to be like the inside and outside of a circle, essentially the same but apparently different when viewed from different perspectives.
Gustav Fechner
On the morning of October 22, 1850, he had the insight that Weber’s work with the j.n.d. could be used to deduce a law relating the mind and the body.
If they occur on opposite sides of the equal sign they are two aspects of the same thing.
He needed to deduce a law that related change in stimulation to change in sensation to show the equality of mind and body.
Gustav Fechner
Based on Weber’s work he noted that as physical change increases geometrically, sensation (what we call perception) increases arithmetically
He needed to develop a mathematical approach to measure the mind quantitatively not qualitatively
Gustav Fechner
Herbart had argued that the mind could not be measured quantitatively and thus psychology could never be an experimental science.
When subjects report an experience it is nominal (absolute thresholds)
When subjects report detecting a difference it is ordinal (difference thresholds)
But the j.n.d as a constant ratio across the broad range of sensations, represents at least interval level of measurement with the j.n.d. as the equal interval scale!!!
Gustav Fechner
The breakthrough;
If a j.n.d. is an arithmetic change (D) in sensation (S) corresponding to a geometric change in physical stimulation (R), and K is the ratio constant, then…
S = K log R, where DR/R = K (Weber’s ratio)
He called his new research program Psychophysics and began research to test his Law.
Gustav Fechner
He developed a number of basic laboratory procedures which we still use extensively in contemporary research including the method of limits, the method of average error and the method of constant stimuli.
Gustav Fechner
Method of Average Error: Every measurement contains error since thresholds are a function of many variables. Therefore the mean and a measure of variability from the mean must be used to approximate true characteristics of measured differences.
Gustav Fechner
Method of Constant Stimuli: Originally based on over 65,000 cases of weight j.n.d. thresholds, he recognized that when repeating the same (constant) stimuli in the test, the subjects would sometimes be correct and sometimes incorrect is stating a difference at or near the threshold.
The difference that produces a 75% correct judgment was the one that identified the threshold.
(We now often use 50%) .
Gustav Fechner
Summarized his 12 years of research in 1860 with the publication of Elements of Psychophysics….”… a text of the exact science of the fundamental dependent relations … of the mathematical and mental, and the physical and psychological worlds”.
The book is recognized as one of the truly original contributions to the emergence of experimental psychology.
Gustav Fechner
It was a remarkable breakthrough refuting Kant who said…” psychology cannot be a science”…because you cannot objectively measure the mind.
It was heralded in it’s time as being the psychological equivalent of the discovery of the law of the lever.
Gustav Fechner
Method of Limits
This was originally called the method of j.n.ds. It was first used by Delezenne (1827) and later by Weber, but it was formally developed by Fechner.
It involves taking very different stimuli and increasing one (ascending method) combined with taking the same stimuli and making one differ more (descending method).
The method recognizes that order effects can create a systematic bias in threshold judgment but that these order effects can be counterbalanced out.
The book was very influential on Wundt, Ebbinghaus and a generation of pioneers in psychophysics, sensation and perception and experimental psychology in general.
To his dismay, he failed to convince many that the mind and body were one. Indeed, the equation shows that one is not the equal of but a log function of the other. Sad but true!
Gustav Rechner
was trained in history and philosophy in England, in the British empiricist tradition.
Hermann
Ebbinghaus
While visiting Paris he bought a used copy of Fechner’s Elements of Psychophysics from a street vendor and read it in his hotel room.
Fascinated by the problem of complex ideas being associations forged from simpler ideas, he saw the rigorous methodology described by Fechner’s work as one readily adaptable to the study of the formation of complex ideas from simple associations experimentally.
Hermann
Ebbinghaus
Starting first with memorizing prose and later inventing the nonsense syllable as a research tool, he worked in his own hotel room, using himself as a subject to study simple learning and memory.
Wundt as we will see, said that it was impossible to experiment on higher mental processes. Within a few years, Ebbinghaus’s work, on learning and memory demonstrated the contrary. The uniqueness of his approach was:
Hermann
Ebbinghaus
British empiricists studied established associations retrospectively while he found a way to study the formation (learning) and retention (memory) of simple associations experimentally.
His work was the first truly “psychological” experiment.
Hermann
Ebbinghaus
He was not a professor, had no academic appointment or laboratory but rather worked in his room as a pure scientist solving a problem of intense interest to himself and later, to the rest of the scientific world.
The precision and control of his work, from Fechner, (always working at exactly the same time of day for each task) yielded results so accurate that contemporary replications of his work using computers and modern controls replicate his original learning and forgetting curves exactly.
Hermann
Ebbinghaus
Examples of his methods and findings include:
Increasing the difficulty of associations increased the frequency of associations (trials) necessary to learn them.
Repetition of the associations to decrease error reporting the averages (Fechner’s method of average stimuli).
Hermann
Ebbinghaus
Running all procedures at the same time of day and establishing rigorous daily schedules. (Experimental control & Fechner’s method of constant stimuli)
Hermann
Ebbinghaus
The nonsense syllable itself was two consonants with a vowel in between them. If any nonsense syllable suggested anything meaningful it was discarded. (Experimental control).
Hermann
Ebbinghaus
a serial list of randomly sampled nonsense syllables were viewed for a fixed duration, and a variable number of trials following which memory for the list was tested .
Using prose took nine trials to memorize a given list to criterion while a comparable nonsense syllable list took 80 trials.
He concluded that the lack of meaningful information made the task approximately nine times as difficult
Hermann
Ebbinghaus
Over learning a list increased the amount of time that could occur between learning and recall for correct recall to occur.
Moreover, percent correct recall was an inverse function of time between learning and recall, demonstrating memory as a function of repetitions during learning as a true experiment on a higher mental process.
Hermann
Ebbinghaus
Based on his work he was given a faculty appointment at the University of Berlin. In 1885 he published On Memory which, based on it’s completeness, rigor and accuracy of the data, is lauded as the single most outstanding achievement in the history of psychology. The book is still cited in contemporary research.
In 1890, he established the Journal of Psychology and Physiology of the Sense Organs to absorb the new literature and compete with Wundt’s “Studien”
Hermann
Ebbinghaus
Although he established no school of his own, he pioneered the field of memory as a quantum leap over what was happening in psychology. It was not just a refinement of the “paradigm” or extension of the zeitgeist, but rather a totally new endeavor.
He was not promoted at Berlin for lack of significant publication after On Memory.
Hermann
Ebbinghaus
He established the first formal laboratory to study Ebbinghaus’ work in a laboratory setting.
G.E. Müller
He invented the memory drum as an apparatus for controlling the presentation of the stimuli.
G.E. Müller
His initial goal was to use introspection to show that Ebbinghaus’ objective mechanical accounts left out important subjective information about the process of memory.
(note here an anticipation of the Act School of Psychology in opposition to Wundt)
G.E. Müller
He reported that subjects actively search for meaning in the nonsense syllables, and conscious sets of readiness (that Wundt had called conscious attitudes) which influenced learning.
He introduced the interference theory forgetting as a process of retroactive interference.
G.E. Müller
Found organization and grouping to be important in memory which led him to argue for a more gestalt, holistic approach (nativistic) and against Wundt’s empiricistic methodology.
G.E. Müller
