Chapter 5 Sensation And Perception Flashcards
Perception
- the process by which the brain organizes and interprets sensory information
- now everyone perceives things the same way
Sensation
Is the detection, by sensory organs, of psychical energy emitted or reflected by physical objects
Where does sensation begin
At the sense receptors
What do sense receptors decide
Is this important enough for us to actually perceive?
Doctoring of specific nerve energies
The principle that different sensory modalities exist because signals received by the sense organs stimulate different nerve pathways leading to different areas of the brain
Anatomical code
- we see and hear with our brain not our eyes and ears
- a way the nervous system encodes our messages
- what the doctoring of specific nerve energies is called
Synesthesia
- a condition in which a sensation in one modality consistently evokes a sensation in another
- ex. smelling colours
- different than memories
What is synesthesia due to
Increased neural connections between sensory areas in the brain or a lack of inhibition between sensory areas
What does Anatomical coding NOT explain
- why for most people our senses are separate
- variations of experience within a particular sense
What do we use the Functional code for
Figuring out what our sensory receptors are sensing
What forms a functional code
Information about:
1. Which cells are firing
2. How many cells are firing
3. The rate at which cells are firing
4, pattern of each cells firing
Absolute threshold
The minimum amount of energy, or quantity of a stimulus required for it to be reliably detected at least 50% of the time it is presented
Difference threshold
Smallest difference between 2 stimuli that a subject can detect
- “just noticeable difference”
Weber fraction example for weight
Webers fraction for weight is 0.02 or 2% difference
- you need to add 0.2lbs to 10lbs to notice a difference
- you need to add 2lbs to 100lbs to notice a difference
Signal detection theory
A psychological theory that divides the detection of a sensory signal into a sensory process and a decision process
Sensory process example
Individuals response
- “I hear something” or “I don’t hear something”
Is there a bear in the woods?
- yes or no
- hear something and there is a bear= hit: right, they did hear the bear
- hear something and there is no bear= false alarm: wrong, they imagined it
- don’t hear something and there is a bear= miss: wrong, they didn’t hear the bear
- don’t hear a bear and there is no bear= correct rejection: right, there is no bear
Hear a bear and there is a bear
Hit: right!
They did hear the bear
Hear a bear and there is no bear
False alarm: wrong!
They must’ve been imagining it
Don’t hear a bear and there is a bear
Miss: wrong!
They didn’t hear the bear
Don’t hear a bear and there is no bear
Correct rejection: right!
There is no bear
Sensory adaptation
Resulting decline in sensory responsiveness when a stimulus is unchanging or repetitious
- don’t want to walk around all day constantly feeling our clothes on our body or our tongue in our mouths
How do we adapt to very intense stimuli
we never completely adapt to it
Adaptation in bigger vs smaller changes
- harder to adapt to bigger changes
- ex. Snap a femur in half= hurt for a long time
- ex. Paper cut= will adapt to the pain in a few minutes
Sensory deprivation tank
- If you have the mindset that it will be good and relaxing then it will be enjoyable and help reduce stress and anxiety
- if you have the mindset that it will stress you out then you will be stressed out
What does sensory deprivation stimulation do
Deprive us of our senses
Types of sensing without perceiving
- Selective attention
- Inattentinal blindness
Selective attention
The process of focusing on selected aspects of the environment while blocking out others
- choosing what you notice and pay attention to
Selective attention
The process of focusing on selected aspects of the environment while blocking out others
- choosing what you notice and pay attention to
Inattentinal blindness
The failure to consciously perceive something you are looking at because you are not attending to it
What is the stimulus for vision
Light
Light
Form of electromagnetic radiation
Hue
Dimension of visual experience specified by colour names
- related to the wavelength of light
Saturation
- colourfulness
- how wide or narrow the wavelength is
- how dark or light the colour appears
Brightness
- dimension of visual experience related to the amount or intensity of the light an object emits or reflects
- corresponds the the amplitude (max height) of the light wave
Sclera
white outer layer of the eye
Cornea
Clear layer that covers the front of the eye
Pupil
Regulates amount of light let into eye
Iris
Round muscle that adjusts the size of the pupil
Lens
Clear structure that focuses light onto back of eye
How the eye gathers light (parts of the eye)
- Sclera
- Cornea
- Pupil
- Iris
- Lens
The retina of the eye
Neural tissue lining the back of the eyeballs interior that contain the receptors for vision
Cones
Concentrated on fovea to produce high-detail, colour vision at our point of visual focus
Rods
On outer regions of retina, provide peripheral vision and are specialized for low light conditions
Dark adaptation
The process by which rods and cones gain sensitivity to low light levels
From light to nerve
- Bipolar neurons
- Ganglion
- Optic disc
- Peripheral vision
Bipolar neurons
Synapse onto photoreceptors
Ganglion
Transmits signals from bipolar neurons to brain
Optic disc
Area on retina that lacks rods and cones
Peripheral vision
Axon tracts from ganglion cells leading to brain
Feature-detector cells
- in the visual areas of the brain
- detect specific aspects of the visual world
What do feature-detector cells detect
Lines at various orientations
What are feature detection cells
- specific groups of cells just above the cerebellum that respond specifically to faces
- cells by the hippocampus help to perceive the environment
- region of cells by the occipital cortex respond stronger to body parts
Optic nerve
Colour vision is determined by three different cone types that are sensitive to short, medium and long wavelength length
Long wavelength colour
Red
Medium wavelength colour
Green
Short wavelength colour
Blue
Trichromatic theory
Combined activity of all three cone types generates a unique signature associated with each perceived colour
- even colours without corresponding wavelength
Opponent- process theory
We perceive colour in terms of opposite ends of the spectrum
- (red to green), (yellow to blue), (white to black)
Opponent process cells
- in the retina and thalamus
- respond in opposite fashion to short and long wavelengths of light
Excited by red =??
Inhibited by green
Excited by green =??
Inhibited by red
Excited by blue =??
Inhibited by yellow
Excited by yellow =??
Inhibited by blue
What colours can we not see
Redish green and blueish yellow
What do opponent-process cells that are inhibited by a particular colour produce
A burst of firing when the colour is removed
- just as they would if the opposing colour were present
Opponent-process cells that fire in response to a colour stop firing when…
The colour is removed
- just as they would if the opposing colour were present
Gestalt psychologists
- started bringing forward optical illusions
- were among the first people to organize the world visually into: meaningful units and patters
gestalt principles
Describe strategies used by the visual system to group sensory building blocks into perceptual units
Figures and backgrounds
- idea that objects or “figures” in our environment tend to stand out against a background
- issues arise when we have a tough time distinguishing between what is the figure and what is the background
- we see something different depending on what we were thinking about at the time
Proximity
We think things should be grouped together based off of where they are located
Similarity
We think things like colours and shapes should be grouped together
- ex. Sports team (jersey)
Continuity
Refers to the perceptual rule that lines tend to be continuous rather than abruptly changing direction
- our brains like things that flow smoothly
Principle of closure
People tend to fill in blanks to perceive a complete object whenever an external stimuli partially matches that object
Dorsal stream functions
- guides interaction with objects
- depth and motion perception
Where does the dorsal stream extend from
Visual cortex to the parietal lobe
Do dorsal streams work together or separate
- can work independently of each other but are generally used together
Binocular depth cues
Distance cues that are based on the differing perspectives of both eyes
Convergence
Occurs when the eye muscles contract so that both eyes focus on a single obejct
Retinal disparity
The difference in perspective provided by each eye
Stereopsis
Sense of depth
Monocular cues
Used to see anything further than 50 feet
- depend on only one eye
Interposition
When an object is interposed between the viewer and a second object, the first object is perceived as being closer
Linear perspective
When 2 lines known to be parallel appear to be coming together or converging, the imply the existence of depth
- ex. Sides of bridge look like they are getting closer together the father away they are from you
Motion parallax
- When an observer is moving, objects appear to move at different speeds and in different directions
What happens to closer objects in motion parallax
the closer it is the faster it seems to move
Do close objects seem to move backwards or forwards in motion parallax
Appear to move backwards
Do distant objects appear to move backwards or forwards in motion parallax
They appear to move forward
Relative size
When all shapes are the same just different sizes, we perceive the smaller ones as farther away
Relative clarity
Objects that appear clearer and more sharply defined are perceived as being closer and objects that are hazier and less distinct are perceived as father awat
Texture gradients: density
textures appear more spread out and detailed when closer but become more compact and less distinguishable with distance
Texture gradients: size
Elements of the texture appear larger when nearer and smaller as they move farther away
Texture gradients: clarity
Closer textures are clearer, while distinct ones tend to blur together
Light and shadow
Refer to depth perception cues where the way light interacts with objects creates shadows and highlights
- helping the brain interpret the 3D form, texture and spatial relationship of objects in an environment
Illumination
Surfaces facing the light source appear brighter, while surfaces facing away are darker
Shadow
Cast shadows and shading provide information about the relative positions of objects and their distances from the light source
Shape and contour
The gradient of light and shadow on an object reveals its curvature or flatness
Ventral (‘what’) stream
Extends from visual cortex to temporal lobe
What is the ventral (‘what’) stream responsible for
- object and face recognition
- fusiform face area
- pareidolia and prosopagnosia
Pareidolia and prosopangnosia
Can’t recognize people faces, especially if they look similar
Greenie experiment
Fusiform face area responsible for visual expertise
