Psych1000 Day 14 - Sensation
- What do Weber fractions tell you about sensation?
- Can we perceive subliminal? subliminal messages?
- How does the visual system work?
How do we perceive world around us?
- Psychophysics: ex. how do we code senses psychologically?
- Psychophysiology (receptor level, what happens to the eye?)
Psychophsyics: relation between physical stimulus & psychological response
Fechner: “father of psychophysics:
- Determined a just noticeable difference (JND)
- It’s hard to measure psychological intense, BUT you can measure the difference of sensitivity
- Ex. turn the light on, you tell me your sense, turn the intensity of light higher, you tell me the difference
Threshold: the value of stimulus characteristic required to produce some response
- Absolute threshold are the lower limit of the threshold
- Ex. vision: candle flame at 50 km on clear dark night (most sensitive sense in a human)
- Hearing: tick of an old watch @ 6m (second most sensitive sense in human)
- Taste: tsp of sugar in 8L of water
- Smell: 1 drop of perfume in a 6rm apt
- Touch: wing of a fly falling on check from 1cm
- Difference threshold: amount of change that’s necessary for JND
o ex. how much change you need to notice the difference
- So what’s the relation between psychological stimulation and actual stimulation?
o Ex. brightness & perceived brightness
o This is NOT a 1:1 relation
Ex. doubling brightness does NOT mean you get doubling in perceived brightness
- **Weber’s Law: size of difference threshold relative to physical intensity of test is constant
- = C (size of difference of different threshold in relation to the intensity of the stimulus is constant)
o If I = 50dB, JND = 55dB
o 55-50/50 = 1/10 = C
o Constant for this stimulation situation is 1/10
o You can predict other JND’s
ex. what’s a JND @ 100 dB?
ΔI /100 = 1/10
ΔI = 100
A JND would occur @ new test + 10 = 110 dB OR
New test – 10 = 90 dB
o Note: the value of JND is NOT constant, but the relative difference is constant
- Can compare sensitivity of difference systems
o The smaller the ΔI, the better (the more sensitive) if the constant
- Vision (brightness) = 1/60
- Kinesthesis (weights) = 150
- Pain (thermal) = 1/30 Psych1000 Day 14 - Sensation
- Audition (mid Pitch; Mod. Loud) = 1/10 (more sensitive to low frequency than high pitches)
- Pressure (skin) = 1/7
- Smell (India rubber) = ¼
- Taste (salt) = 1/3<<