1. Laboratory from perception
Engineering Psychology
Cognitive processes
Laboratory from perception
Jakub Jura

2. Lab 1 - Perception Emmert law Weber law Fechner law
Discrimination Thresholds
Haptic sensitivity
Blind spot

3. Emmert’s law Emil Emmert (1844 - 1911)
Emmert law: The afterimage size changes proportionally with its distance from the observer. a a’ l l’

4. Weber law
Ernest Heinrich Weber  (1795–1878)
Experiment with weight difference
Just noticeable difference (jnd) between two weights was approximately proportional to the mass of the weights
I = kw* I
I … Base intensity (Total weight)
I … Discrimination threshold (Weight difference)
kw Constatnt (Weber Fraction)
We can‘t perceive the intensity of stimulus directly, but in relation to the reference value.

5. Fechner law Gustav Theodor Fechner (1801–1887)
Dependence of sense impression on the intensity of stimulus is logarithm.
P = k * ln (S)
P … percept
k … constant
S … stimulus

6. Fechner law

7. Weber-Fechner law Weber-Fechner principle in the acoustics:
LI=10 log (I/I0)
Lp=20 log (pe/pe0)
L … Level of intensity
I … Intensity
P … Aacoustic pressure
I0, pe0 ... Minimal perceived value

8. Discrimination threshold
In acoustics

9. Haptic sensibility Tactile compasses The brain – projection zone.
Skin surface and brain surface.

10. Blind spot
Close the right eye. Leave your head in the central position.
Look to the cross, by the left eye.
Approach your head to the paper.
The circle disappears in a given distance.