PSY 102 Lecture Notes - Lecture 4: Tropicana Products, Subjective Constancy, Color Constancy

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15 Aug 2016
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PSY102 Lecture 4
Sensation and Perception
How we sense and conceptualize our world?
Sensation: detection of physical energy (stimuli) by sense organs (eyes, ears, nose, skin, tongue)
Sense organs relay info to the brain, simultaneously and changes, and brain has to adjust
Perception: brain’s interpretation from sense organs
Gives meaning and coherence to raw data
Our perceptions don’t always match reality
e.g., filling in, reconstruction, interpolation
Sensation: Bottom-up process by which our sensory organs receive and replay sensory input.
Perception: Top-down way our brains organize and interpret sensory input.
Transduction
Converts external stimuli into electrical signals with neurons
Done by sense receptors specific to certain stimuli (sight, smell, touch)
Sensory adaptation: activism is greatest when a stimulus is first detected
Response diminishes over time to conserve energy (cognitive misers - we don’t need to
response)
Psychophysics (Fechner)
Study of how we perceive sensory stimuli based on their physical characteristics
Absolute threshold: the lowest level of a stimulus that we can detect 50% of the time.
Just noticeable difference: the smallest change in the intensity of a stimulus that we can detect
The stronger the stimulus, the bigger the change in intensity needed for us to notice it.
Just Noticeable Difference and Marketing - they do not want to do dramatic changes to not to
upset people
https://rly819.wordpress.com/2015/05/18/a-just-noticeable-difference-or-not/
Cadbury chocolate and Tropicana orange juice
Marketers are concerned that:
Negative changes are not readily discernible: (such as price increases)
Updated packaging or lower prices are readily discernible (at or just above JND)
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How stimuli are detected under different conditions
Signal-to-noise ratio: harder to detect a signal clearly as background noise increases. Much
harder to notice a stimuli when the outside noise is loud. Trying to tune out background noise.
Response biases: hits and misses in signal detection. Stimulus is not happening.
Cross-Model Sense
McGurk effect: hearing audio of one syllable, while watching a video of someone articulating a
different syllable, produces an experience of a third sound.
Rubber hand illusion: sense of touch and sight can interact to produce a false perceptual
experience.
Synesthesia
Experience of cross-model sensations by a small number of people
More common among children, fine arts students, musicians
Grapheme-colour synesthesia: numbers associated with specific colours
Lexical-taste synesthesia: words have tastes associated with them
When Senses Meet Brains
After transduction , the brain must organize all that sensory input into meaningful categories.
Our brains piece together a puzzle: (all of theses have to come together)
What is presently going on in our sensory field
What just happened in our sensory field
What we remember from our past experiences
MIDTERM!!!
Parallel Processing
Paying attention to multiple sense modalities simultaneously
Bottom-up processing: construct a whole from its component parts
Moves from visual cortex to association cortex
Top-down processing: conceptually-driven processing influenced by our beliefs and
expectations (the world as it is)
Moves from association cortex to the visual cortex
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