Ernst Weber & Gustav Fechner -- psychophysicists Hermann Ebbinghaus -- memory 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: 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. 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.
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. |