Weber and FechnerWeber and Fechner

PsychophysicsPsychophysics

AfterimagesAfterimages

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

Try them on the classroom computers. Try them on the classroom computers. Note when you see color etc…Note when you see color etc…

Weber's LawWeber's Law

(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 Let us suppose that we are working w/ the

perception of differences in weight, and perception of differences in weight, and the measure is paperclips. Let us suppose the measure is paperclips. Let us suppose that: S1=2, S2=4, then K=1 that: S1=2, S2=4, then K=1

How many paperclips do you need to feel How many paperclips do you need to feel they were heavier than 4 paperclips? they were heavier than 4 paperclips? Etc…Etc…

Sensation-Perception dataSensation-Perception data

Sensation (S)Sensation (S)(geometric scale)(geometric scale) 22 44 88 1616 3232 6464 128128

Perception (P)Perception (P)(arithmetic scale)(arithmetic scale) 11 22 33 44 55 66 77

P=log S in base (K+1)P=log S in base (K+1)

jnd Sensation-Perception jnd Sensation-Perception graphgraph

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Weber's function, mind and Weber's function, mind and bodybody

S= sensation = sensory organ = bodyS= sensation = sensory organ = body P= perception = mindP= perception = mind

Hence:the mind and the body are different and Hence:the mind and the body are different and separate, follow different lawsseparate, follow different laws

And: The mind and the body are connected by a And: The mind and the body are connected by a mathematical relationship.mathematical relationship.

Thus: The mind can be studied scientifically. Thus: The mind can be studied scientifically. Psychology can be a science.Psychology can be a science.

Yippee!Yippee!

The The nightviewnightview and the and the dayviewdayview can be can be reconciled.reconciled.

PsychophysicsPsychophysics

The study of the relation between the body The study of the relation between the body and the mind, in matters of sensation and and the mind, in matters of sensation and perception.perception.

Fechner is the founder of this branch of Fechner is the founder of this branch of psychology.psychology.

EstheticsEsthetics

What makes something beautiful?What makes something beautiful? Is it a question of proportions?Is it a question of proportions?

Fechner is one of the first people to address Fechner is one of the first people to address the question experimentally.the question experimentally.

The endThe end