Ebbinghaus said this because psychology’s questions go back to the ancients

Ernst Weber & Gustav Fechner -- psychophysicists

• Ernst Weber & Gustav Fechner -- psychophysicists

• Hermann Ebbinghaus -- memory

• Franz Brentano

• Carl Stumpf

• Oswald Kulpe

Weber published “De tactu” describing the minimum amount of tactile stimulation needed to experience a sensation of touch – the absolute threshold.

• Weber published “De tactu” describing the minimum amount of tactile stimulation needed to experience a sensation of touch – the absolute threshold.

• Using weights he found that holding versus lifting them gave different results (due to muscles involved).

• He used a tactile compass to study how two-point discrimination varied across the body.

• On the fingertip .22 cm, on the lips .30 cm, on the back 4.06 cm.

Weber studied how much a stimulus must change in order for a person to sense the change.

• Weber studied how much a stimulus must change in order for a person to sense the change.

• How much heavier must a weight be in order for a person to notice that it is heavier?
• This amount is called the just noticeable difference JND
• The JND is not fixed but varies with the size of the weights being compared.

• JND can be expressed as a ratio:

• where R is stimulus magnitude and k is a constant and R means the change in R ( usually means change)

Fechner related the physical and psychological worlds using mathematics.

• Fechner related the physical and psychological worlds using mathematics.

• Fechner (1860) said:

• “Psychophysics, already related to physics by name must on one hand be based on psychology, and [on] the other hand promises to give psychology a mathematical foundation.” (pp. 9-10)

• Fechner extended Weber’s work because it provided the right model for accomplishing this.

Fechner called Weber’s finding about the JND “Weber’s Law.”

• Fechner called Weber’s finding about the JND “Weber’s Law.”

• Fechner’s formula describes how the sensation is related to increases in stimulus size:

• where S is sensation, k is Weber’s constant and R is the magnitude of a stimulus

• The larger the stimulus magnitude, the greater the amount of difference needed to produce a JND.

• He used catch trials to study guessing.

His methods are still used in psychophysics.

• His methods are still used in psychophysics.

• Ideas from signal detection theory have been applied to a wide variety of other topics.

• Threshold for criminal behavior, scenic beauty.

• Scaling techniques, including rating scales, were placed on a sound scientific basis, especially by S.S. Stevens later work, continued by Luce & Narens.

• His speculations about split-brain studies were confirmed by Sperry.

Ebbinghaus was inspired by finding a copy of Fechner’s “Elements of Psychophysics.”

• Ebbinghaus was inspired by finding a copy of Fechner’s “Elements of Psychophysics.”

• He wanted to apply Fechner’s methods to study of higher mental processes.

• In 1877, he began developing procedures for studying memory.

• His major work, “Fundamentals of Psychology,” is dedicated to Fechner – “I owe everything to you.”

Ebbinghaus had no mentor to teach him techniques so he developed his own, highly original methods.

• Ebbinghaus had no mentor to teach him techniques so he developed his own, highly original methods.

• He had no lab, no access to subjects, so he performed most experiments on himself.

• He followed rigorous experimental rules and spent 4 years replicating his first series of experiments.

• These were well received and widely recognized.

• His nonsense syllables were developed to avoid word familiarity, using a permutation formula.

• 19 consonants, 11 vowels, 11 consonants = 2299

First, he studied the relationship between the amount of material to be memorized and the time needed to learn it to complete mastery.

• First, he studied the relationship between the amount of material to be memorized and the time needed to learn it to complete mastery.

• His measure was number of repetitions needed.

• Second, he studied the effects of different amounts of learning on memory.

• His measure was savings – repetitions needed to relearn the original items after a delay.
• As repetitions increase, so does relearning time saved – overlearning helps.

His best known experiment studied the effects of passage of time on memory – his forgetting curve.

• His best known experiment studied the effects of passage of time on memory – his forgetting curve.

Ebbinghaus studied the relative effects on memory of spaced versus massed practice, part versus whole, and active versus passive learning.

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