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Lecture 4

PSY 105 Lecture Notes - Lecture 4: Umami, Visual Cortex, Dysautonomia

Course Code
PSY 105
Kristin Vickers

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Chapter 4: Sensation and Perception
- a subjective experience of an aspect of a sense of other than the one being stimulated. A patient of synesthesia may see letters that are
in black as different colours.
- Psychological and neurobiological reality
- brain regions for different sensory modalities cross-activate each other
The power of Perception
- Basketball tracking test: focus on people in white passing basketball (there are also people in black passing basketball) and a gorilla
passes by (most people don’t see it, because they are selectively looking at the basketball)
- Door study: 50% of people are attention/change blindness. Ex. ask for direction and person giving directions don’t notice person
changes when door passes by.
Basics of sensation and perception: *these 2 are related but separate events
- Sensation- the act of using our sensory systems to detect environmental stimuli
Raw sensory data:
Vision – light waves
Hearing- sound waves
Smell- airborne chemicals
Taste- food chemicals
Touch- pressure
- Perception- recognizing and identifying sensory stimulus
Features of sensation and perception: What do we need to do to the raw sensory data so that our brain can understand it?
-Sensory receptor cells: specialized cells that convert a specific form of environmental stimuli into neural impulses
-Sensory transduction: the process of converting a specific form of sensory data into a neural impulse that our brain can read.
-Absolute threshold is the smallest amount of a stimulus that one can detect. Ex. what is the dimmest light you can see? Or what
if someone touches you very lightly. In other words, this is the difference between “sensing” and “not sensing”
Difference threshold:
-Just noticeable difference (JND): the minimal change in a stimulus that can just barely be detected
-Weber’s Law: the just noticeable difference of a stimulus is a constant proportion despite variations in intensity. Ex. 100 gm –
then 2 gm difference or 1000 gm- 20 gm notice
Processing Sensory information
-Bottom- up processing- the raw sensory data is sent to the brain and your brain uses all of the data to build a perception.
-Top-down processing- you use previously learned information to help recognize and interpret the data coming into your brain
Top-down processing:
-The process by which we organize small pieces of sensory experiences into meaningful wholes
-Gestalt principles: visual information is organized into coherent images; gestalt means whole or totality; the whole is more
than the sum of its parts. Ex. closure- we tend to fill in small gaps in objects so that they are still perceived as whole objects
Perceptual set: is the readiness to interpret a certain stimulus in a certain way (picture of young and old women in a picture)
How do we smell? - Olfactory sense
-Chemicals, called odorants (airborne chemicals detected as odors), are carried through the air and reach the 5 million
receptors cells located at the top of each nasal cavity. (Olfactory receptor neurons)
-The receptor cells turn that molecule into a neural impulse (transduction) and sent that impulse to the olfactory bulb (small
center in the brain)- lock and key binding
How do we taste? – Gustatory sense
-Chemical substances in food dissolve in saliva and fall into the crevices between the bumps (papillae) of the tongue.
The bumps hold our taste buds
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