PSYB57 Final: Perception
Perception
Taking in information through sensations to figure out the world.
2 Stages of perception:
1. Sensation: measuring, converting of physical stimuli to neural codes by the peripheral nervous system.
2. PerceptionL processing/interpretation of neural codes to do something useful with it.
Exteroception
measuring and interpreting of external enviornmental infromation
Vision: light, smell: chemicals, taste: chemicals, touch: heat/pressure/vibrations, hearing: vibrations
Introspection
Looking inwards at your own internal state.
equalibriaception, nociception, propriaception.
Proprioception
Sense of where our limbs are in space.
Nociception
Sense of pain due to damage
Equilibrioception
Sense of balance
4 sensory receptors:
Chemioreceptiors: mouth, nose and skin
Photoreceptors: eyes
mechanoreceptors: skin, ears, blood vessels.
Thermoreceptors: skin, organs
Basic properties of all sensory modalities
Transduction, transmission to the brain, processing for behavioural use.
Process of vision
Goes through the cornea
Goes through the pupil through the iris
Goes to the retina
The photoreceptors at the back are rods and cones
Optic nerve to the brain.
Visual heiarchy
Retina processes lightness/darkness
Early cortex processes edges
Middle cortex processes shapes
Late cortex processes specific objects.
Different cortext regions respond to different stimuli
Fusiform face area (FFA) show activtity during facial recognition.
Lateral occipital cortex (LOC) show activity for object recognition
Visual agnosias
Disability where it is difficult for someone to recognize certain types of objects.
Prosopagnosia
People can't recognize someone's face.
Semantic agnostics
People can't recognize everyday objects.
Brain regions may not be specialized, but the proccessing is.
FFA concerned with faces because it specializes for visual expertese and activates for faces because being facial experts are important.
Different streams of information
Dorsal stream goes up to the peripheral lobe, looks at location.
Ventral stream goes down to the temporal lobe, looks at identification
Division can be based on what information is used for and what is being taken in
When asked to do 2 tasks that both determin orientation, perceptual task ability only affected when action is not involved because the dorsal stream took over, auggesting that is what the dorsal stream is for.
Auditory sensory system
Designed to transmit properties of sound waves to turn them into neural signals.
Process
Pinna
Ear canal
Eardrum
Ossicles
Cochlea
Basilar membrane
Complex ear structure purpose
All to amplify sound, because the basliar membrane is submerged in liquid, which blocks a lot of sound. It is submerged in liquid to mimic the state when humans have not evolved to be on land.
Hairs in coil shape
Totonic map, where hairs respond to lower freqencies the further along you get into the coil.
Sound is systematically organized when it gets passed along into the brain.
Auditory cortex
Begins at primary auditory cortex in the temporal lobe that listen to distinct stimuli like rhythm and pitch.
The goes to dorsal and ventral stream.
Sound waves
Different patterns coming from different objects that allow you to ifer properties of the world.
Frequency
Wavelength.
Measures how far waves are distanced from eachother.
High frequences means shorter waves meaning stemming from a thin and small object,
Bive versa for high frequences.
Amplitude
Height of crests/waves
Higher means louder sound.
Olfaction
Sense of smell measuring chemicals travelling through the air.
Gestation
Sense of taste measuring chemicals ingested in the mouth
Timeline of senses
Taste and small developed first and the others are extensions of them
Process of taste
Little structures called tastebuds have receptors for each of the 5 tastes. They bind and information goes to the primary gistatory cortext made out of lateral sulcus and frontal lobe.
Process of smell
Olfactory epithelium has a nasal cavity with different receptors for different chemicals that go to olfactory bulb which people don't know what is used for but projects to other parts of the brain.
flavour
Smell and taste are esstial to eating and they make up flavour.
Mechanoreceptors
Spread on skin responds to physical stimuli.
4 types.
Cortical homunculus
Creepy sensory brain map
Bottoms-up processing
Sensation/what you are seeing with no other information needed.
Looking at things for exactly what they are.
Top-down processing
Leveraging knowledge/expectation that are not sensory stimuli to process.
Interpretations could be driven by expectations and past events.
Phonemic restoration effect:
brain fills in missing audio information to finish unheard speech based on expectations from prior experience.
How we understand enviornment:
Sensations
Perceptions
Transductions
Sensations
Features of enviornment used to create understanding of the world.
Perceptions
Combination of sensations mixed in with prior knowledge
Transductions
Process where sensations are translated to electrochemical transmssion of the brain.
McGurk Effect
We tend to look at people's lips because they inform you about the sound created.
You hear different sentences depending on the text you're reading tha tmight sound similar.
Colour blindness
imability to see green/red colours
Ishihara Test
Checks for colour blindness
Opponent process
When cells fire in an opposing fashion.
If you stare at something green and then look away quickly, you might see the same image in red because the green cells are so charged up when the stimuli is gone you automatically see the opposite.
Properties of visual stimuli:
Image segmentation: ability to seperate objects from one another.
Depth perception: what is near and what is far.
Object recognition: matching stimuli with a representation of something
Edge detection
Finding edges of an object to differentiate it from others.
Visual systems might override bottoms-up output of an edge detector based on top-down knowledge of object properties.
Gestalt principles
For helping with image segmentation:
Figure-ground
Groups-figure assignment
Proximity
Similarity
Common Fate
Continuation
Closure
Visual grouping
Depth cues
Object blocking: stuff in front is closer than stuff being cut off.
Motion parallax: stuff closer to you will seem to move faster.
Binocular disparity: you must go cross-eyed to see something close and straight-eyes to see something far.
Template modeling
Matching an object stored in memory point-by-point, but not everything looks exactly the same.
Identification
Ability to identify the same object across variations
Classification
recognizing a member as part of a category even if one has never encountered a specific example.
There are features of the object that remains the same across variations
Object recognition and context
Contexts lets you assume what it is with top-down processing.
Constructive Perception Model
Perception constructs a stable mental model of the external world and behavioural decisions are based on that model, not sensations itself.
AKA unconcious inference
Direction Perception Model
Sensory stimuli is what is used to suide behaviour.
Dominent Constructive Theory of Perception
Sensory data is used as evidence to infer about external conditions
Illusions
Stimuli is often ambiguous and can be consistent with a lor of sensory evidence.
When our inferences about the enviornment is wrong.
Proof that we make guesses.
Bi-stable stimuli
Stimuli that can shift in perception.
We are changing our inferences when looking at these.
Perception of stimuli depends on the process as well as the stimuli itself.
Image segmentation and the 2 processes
Bottoms-up approach to infer edges and often overridden by top-down appraoch when not useful.
Figure-ground assignment
Deciding what is the object and what is the background in an image.
(F/g)
3 biases in figure-ground assignment
Convexity: we like the figure to be pertruding outwards.
Symmetry: we like the image to be symmetrical.
Size: we like the figure to be the small stuff.
Visual grouping
Putting seperate objects into the same category.
Common fate, similarity, proximity.
Stereopsis
When you don't develop binocular disparity
General recognition
Ability for comuters to classifying a class of different objects.
Scene schema
An idea of what is usually in a specific setting.
Convolutional neural network
CNN
artifical neural networks that classify images based on learning features of images that can appear in different locations of that image.
Convolutions
Operation where an imager undergoes a mathematical equation that outputs a different image.