German physiology psychophysics and science of mind 2

Psychophysics

• was one of the first areas of systematic psychological research

Psychophysics is the study of the relationships between the properties of stimuli and the psychological impressions of those stimuli.

Solipsism

we can only know our own experience

Realism

we perceive the world as it is

What did psychophysics demonstrate?

that relationships between external reality and perception were lawful AND studies of thresholds and derivation of psychophysical functions demonstrated that perception IS NOT always realistic

Psychophysics advanced measurement of behavior

Psychophysicists pioneered the quantification of mental processes.

– They demonstrated lawful relationships between physical stimuli and the psychological impressions of stimuli.

Weber (1795-1878)

Weber is a father of experimental psychology

A physician, specializing in anatomy and physiology (where he made important findings about vagus nerve, and development of male genital-tract, Müllerian ducts)

• He demonstrated that different locations on the body have different two-point thresholds

Weber’s Illusion refers to:

The illusory experience of two points when these are moved over insensitive or sensitive areas of the skin.

What did Weber demonstrate?

In the 1840s, Weber pioneered research into difference thresholds, identifying the just noticeable difference (JND) between stimuli in a variety of modalities.

– JND is a constant proportion of stimulus magnitude, rather than an absolute amount

Weber formulated the first valid quantitative generalization in psychology

Fechner 1801 - 1887

Physician and physicist, professor of physics at University of Leipzig

• Permanently damaged his vision in 1839, which caused a long episode of mental and physical illness

• 1860 published Elements of Psychophysics: founded psychophysics as a scientific and quantitative way to measure the relationship between the physical world (stimuli) and the human mind (sensations)

Fechner did what to Webers formula?

Discovering Weber’s work, he reformulated Weber’s formula and called it Weber’s Law

• S = k log R

• Perceived intensity (S) equals a constant times the log of the physical intensity (R)

Fechner developed methods still in use

The method of limits, The method of constant stimuli, The method of average error

• Fechner's methods are still taught and are used in studies of perception.

The method of limits

Used to determine thresholds, JNDs, uses ascending and descending series of magnitudes or differences

The method of constant stimuli

stimuli, or stimulus pairs, are presented in random order

The method of average error

participants adjust a comparison until it matches a standard

what is JND?

JND stands for Just Noticeable Difference (also called the difference threshold).

In psychology and psychophysics, it is the smallest change in a physical stimulus (like light, sound, weight, or temperature) that a person can detect 50% of the time.