1. Weber and Fechner Psychophysics

2. Gustave Fechner (1801-1887) Son of a Lutheran pastor Son of a Lutheran pastor Studied medicine, then his interests turned to physics Studied medicine, then his interests turned to physics 1834: appointed professor at Leipzig University --becomes interested in studying sensation. 1834: appointed professor at Leipzig University --becomes interested in studying sensation. Is known for his study of AFTERIMAGES Is known for his study of AFTERIMAGES

3. Afterimages Examples of some of the illusions with which Fechner worked. Examples of some of the illusions with which Fechner worked.some of the illusions some of the illusions

4. Looking into the sun Vision problems from looking at the sun through colored glasses Vision problems from looking at the sun through colored glasses Depression. Depression. Struggle between the prevalent scientific "mechanistic" view of the world (nightview) and his own view that the world is alive and conscious as well (dayview) Struggle between the prevalent scientific "mechanistic" view of the world (nightview) and his own view that the world is alive and conscious as well (dayview)

5. Dr Mises and Dr Fechner Fechner wrote under the pseudonym of Dr Mises to express his "dayview" and satirize the "nightview" Fechner wrote under the pseudonym of Dr Mises to express his "dayview" and satirize the "nightview" For example, in The Little Book of Life after Death Dr Mises speeks of human existence as occurring in 3 stages: For example, in The Little Book of Life after Death Dr Mises speeks of human existence as occurring in 3 stages: Sleep in mother's womb Sleep in mother's womb Alternating between sleep and awake (+ glimpses of stage 3) Alternating between sleep and awake (+ glimpses of stage 3) Becoming a part of the Supreme spirit. Becoming a part of the Supreme spirit.

6. Connecting body and mind Fechner's view is one of DOUBLE ASPECTISM Fechner's view is one of DOUBLE ASPECTISM He wanted to be able to demonstrate a connection between body and mind, so scientific people could accept the existence of mind. He wanted to be able to demonstrate a connection between body and mind, so scientific people could accept the existence of mind. He saw Weber's law that connects sensation and perception as doing this. He saw Weber's law that connects sensation and perception as doing this.

7. Webers law Highlights the fact that SENSATION (body-linked) and PERCEPTION (mind linked) progress in two different and distinct ways Highlights the fact that SENSATION (body-linked) and PERCEPTION (mind linked) progress in two different and distinct ways And are linked one to the other by a mathematical equation And are linked one to the other by a mathematical equation Hence, body and mind are both distinct and connected. Hence, body and mind are both distinct and connected.

8. Weber's Law: the jnd (S2-S1)/S1 = K, where S2-S1= jnd (S2-S1)/S1 = K, where S2-S1= jnd Let us suppose that we are working w/ the perception of differences in weight, and the measure is paperclips. Let us suppose that: S1=2, S2=4, then K=1 Let us suppose that we are working w/ the perception of differences in weight, and the measure is paperclips. Let us suppose that: S1=2, S2=4, then K=1 How many paperclips do you need to feel they were heavier than 4 paperclips? Etc… How many paperclips do you need to feel they were heavier than 4 paperclips? Etc…

9. Sensation-Perception data Sensation (S) (geometric scale) Sensation (S) (geometric scale) 2 4 8 16 16 32 32 64 64 128 128 Perception (P) (arithmetic scale) 1 2 3 4 5 6 7 P=log S in base (K+1)

10. jnd Sensation-Perception graph

11. Weber's function, mind and body S= sensation = sensory organ = body S= sensation = sensory organ = body P= perception = mind P= perception = mind Hence:the mind and the body are different and separate, follow different laws Hence:the mind and the body are different and separate, follow different laws And: The mind and the body are connected by a mathematical relationship. And: The mind and the body are connected by a mathematical relationship. Thus: The mind can be studied scientifically. Psychology can be a science. Thus: The mind can be studied scientifically. Psychology can be a science.

12. Psychophysics The study of the relation between the body and the mind, in matters of sensation and perception. The study of the relation between the body and the mind, in matters of sensation and perception. Fechner is the founder of this branch of psychology. Fechner is the founder of this branch of psychology. 1860, the date of publication of Elements of Psychophysics is sometimes suggested as the birth date of psychology as a science. 1860, the date of publication of Elements of Psychophysics is sometimes suggested as the birth date of psychology as a science.

13. Esthetics What makes something beautiful? What makes something beautiful? Is it a question of proportions? Fechner is one of the first people also to address the question experimentally. Is it a question of proportions? Fechner is one of the first people also to address the question experimentally.

14. The end