PSYCH 10 Lecture Notes - Lecture 4: Interposition, Stereopsis, Detection Theory
Sensation and Perception
- Sensation – detecting physical stimuli and sending this info to the brain
- Perception – processing, organizing, and interpreting sensory info
- Transduction (sensation → perception)
o The process of converting one form of energy to another
o Sensory transduction converts physical stimuli to neural impulses
o The senses
▪ Receive
▪ Transform
▪ Deliver
- Bottom-up processing: perception based on the physical features of the stimulus
o From basic level up to more complex
- Top-down processing: how knowledge, expectations, or past experiences shape the interpretation of
sensory information
o The context and our expectations affect perception
- Sensory threshold
o Absolute threshold: the minimum amount of stimulation needed to detect a stimulsus 50% of
the time … ore tha hae!
▪ “tiuli elo this threshold are alled suliial
▪ Ex: a teaspoon of sugar dissolved in 2 gallons of water
o Difference threshold: the minimum difference between 2 stimuli needed to detect a difference
between them 50% of the time
▪ just otieale differee
o Weer’s La: i order to e pereied as differet, the itesit of 2 stiuli ust ar a
constant proportion of the intensity of the original stimulus
▪ As intensity increases, we get less sensitive to change
▪ 1 oz vs 2 oz – easy to tell the difference
▪ 20lb 1oz vs 20lbs 2oz – harder to tell the difference
- Signal detection theory: predicts how and when we detect the presence of a faint stimulus (signal)
amid background noise (other stimulation). Assumes that there is no single absolute thresehold and
detection depends on:
o Perso’s eperiee
o Expectations
o Motivation
o Level of fatigue
o Consequences of missing → radiologists
- Payoff matrices for SDT
- Sensory adaptation: diminished sensitivity as a result of constant or recurring stimuli
o Why? So we can pay more attention to new information
1/24/18
- How do we see color?
o Yong-Helmholtz Trichromatic Color Theory: 3 types of cones – respond to red, green, or blue
light
▪ Other colors formed by mixing some combination of the above three
▪ Colorblind people lack one or more types of cones
▪ Men are more colorblind than women
o Opponent process theory: three sets of retinal processes – red/green, yellow/blue, white/black
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