Psychophysics

Question 1

Psychophysics

Answer 1

Psychophysics: study of the relationship between physical stimulus magnitude and their corresponding *psychological sensations. *

Psychophysical Laws: identify absolute thresholds and difference thresholds

1. Absolute Threshold: minimum stimulus needed to produce a sensation.
2. Difference Threshold: smallest increment in stimulus intensity needed to recognize the discepancy between two stimuli.
3. Just Noticeable DIfference (JND): represents psychologically equal intervals while their corresponding physical differences do not.
   
   1. JND for a 15lb weight might be 1 pound but the JND for a 50 lb weight may be 5 pounds.
   2. Remember its stimulus intensity will equal 1 JND but the actual physical amount may be greater than 1.

Question 2

3 Psychophysics Laws:

Weber’s Law

Fechner’s Law

Steven’s Power Law

Answer 2

Weber’s Law: more intense the stimulus the greater the increase in stimulus intensity required fo the increase to produce a JND.

1. If one gram must be added to 10 grams for an increase in weight to be detected, then 10 grams would have to be added to 100 grams for an increase to be perceived. sensation relativity?

Fechner’s Law: extends weber’s law: could determine the precise relationship between the magnitude of a stimulus and the magnitude of the associated sensation. Physical stimulus changes are logrithmically related to their psychological sensations.

1. a person’s experience of stimulus intensity increases arithmetrically as the stimulus intensity increases geometrically.

**Steven’s Power Law: **Weber’s and Fechner’s Laws work well for stimulus intensities w/in the middle range, but not for extreme intensities.

1. Steven’s creates a direct measure of sensation
2. magnitude estimation asks participants to assign numbers to stimuli proportional to their relative sensation.
   
   1. so arbitrary say a tone intensity is 3 and then the second tone will be double volume so it’s assigned a value of 6.
   2. sensation as an exponential function of stimulus intensity.
   3. Steven’s Power Law: predicts by doubling the intensity of a light less then doubles the sensation of the light’s brightness BUT doubling the intensity of electic shock more than doubles the physical sensation.