Problem 3: Psychophysics and signal detection + colour perception Flashcards
formula for difference threshold
(P75% - P25%)/2
four answer categories in a signal detection task
hit: correctly saying it’s there
Miss: incorrectly saying it’s not there
False alarm: thinking it’s there when it is not
Correct rejection: correctly saying it’s not there
what are the two theoretical parameters
sensitivity: ability to distinguish signal from noise
Response criterion: how likely a person is to say yes/no to stimulus
what is a payoff structure
adding incentive to change a person’s motivation, resulting in different answers, without changing the stimulus intensity
what is Weber’s law
DI/s=k
Di = just noticeable difference = threshold for noticing a difference
s = intensity of the standard stimulus
k = a constant, the Weber fraction
k = Di/I
what is the trichromatic theory of colour vision (Helmholtz)
vision is based on three things: colour pigment (wavelengths), cone responding (how do our cones respond to the wavelengths) and colour perception (how de we perceive those responses). The theory states that colour perception depends on the pattern of activity in the 3 receptor mechanisms
how can we see? (cones)
1 cone: no colour vision, only shades of grey
2 cones: colour vision
3 cones: more colour vision
what is a metamerism
two perceptually identical colours are made up of different component (different combinations of wavelengths)
what is the opponent process theory of vision
vision is based the output of three component: Y-B, R-G, B-W spectra. would be proved by afterimages (as one colour causes an afterimage of the opposing colour) and simultaneous colour contrast (surrounding an image with a colour changes the perception of the colour in the surrounded area). Theory was confirmed by the discovery of opponent neurons. §
monochromat (& types)
people who can only see black and white
- cone monochromat: one cone, black and white vision
-rod monochromat: bad vision and colour blindness, bright light even more intense
dichromat (& types)
two types of colour pigments, able to see colour but not all
- protanopia: absence of L-cones
- Deuteranopia: missing M-cones
- Tritanopia: missing S-cones
dichromat (& types)
two types of colour pigments, able to see colour but not all
- protanopia: absence of L-cones
- Deuteranopia: missing M-cones
- Tritanopia: missing S-cones
anomalous trichromat
need 3 wavelengths to discriminate between colour, but cannot discriminate very well between wavelengths that are close together
