Ch.3, Perception Flashcards
Inverse Projection Problem:
the image on the retina could be made by multiple objects and its based on the perception to what to make of the object; top down processing and bottom yup processing help us decide what the object is, NEED BOTH
task of determining the object responsible for a particular image on the retina:
there is no way to reverse/deconstruct the whole of the stimuli: it is presented to your visual system as a whole
Viewpoint Invariance:
people’s ability to recognize an object even when it is seen from different viewpoints
Difference between sensation and perception
Sensation: stimulation of the sensory receptors and organs
Perception: organizing sensory input into representations of the physical stimulus, GIVES MEANING TO SENSORY INPUTS (light of different wavelengths = become colors, sound waves of different frequencies = become pitch, for example giving meaning to a childhood toy)
Depending on how you view something, your perception changes and it can be subject
How Visual Info Enters the Brain
Eye—thalamus—visual cortex (cerebral cortex)
Thalamus:
“relay” station, most sensory info goes through thalamus first, then sends it to the corresponding lobe for that sense, DIRECTION STATION in the medial part of the brain, NOT part of the cerebral cortex
Optic Chiasm:
crossing point where visual info from the right visual field info goes to the left hemisphere at the first entry point of the brain (AND VICE VERSA)
V1-V5 visual processing
V1: primary visual cortex, early stages of processing, lines, spatial frequency, VERY BASIC, contrasts (V2 is kind of an extension of V1)
V3-5 IS VERY SPECIIFC, BEFORE THIS THEY ARE VERY BROAD: V3: where we perceive form/shapes/
V4: color and form (mostly length)
V5/MT: picks up on motion
What happens if you didn’t;t have V1 processing?
IF YOU DONT HAVE V1 YOU CAN’T CONSCIOUSLY PERCEIVE THE OBJECTS, BUT YOU CAN STILL IDENTIFY THE OBJECT;
Damage to the adult, primary visual cortex (V1) causes severe visual impairment that was previously thought to be permanent, yet several visual pathways survive V1 damage, mediating residual, often unconscious functions known as “blindsight.?
What pathway
WHAT AM I SEEING?
Ventral (bottom) part of the brain through the temporal part of the cortex (ALL AREAS ARE INTERCONNECTED)
Travels through V3, V4, and V5
Occipital to temporal lobe
Vision for perception: identifies the objects and gives them a label
Different aspects of object perception
Goes through fusiform area, which also aids in facial recognition
“How Pathway”
OCCIPITAL TO PARIETAL
Vision for action because it guides our movements
Allows us to interact with the object we see: doesn’t care about the identity of the object, but cares about spatial judgement
Visual guidance for movements top of the brain
Titchener Illusion
Report the size difference between circles when theyre surrounded by larger circles
Visual effect is larger for the visual system than the motor (MOTOR SYSTEM IS MUCH LESS IMPACTED BY THE ILLUSION THAN THE VISUAL SYSTEM)
Bottom-Up Visual Perception, Low Level to High Level
Bottom up processing: begin at the bottom with the physical stimulus (observable form/pattern), then move up to higher-order cognitive processes EMPHASIS ON PHYSICAL STIMULI
BASIC SENSORY ELEMENTS ATE COMBINED TO PRODUCE A PERCEPTION THAT WE EXPERIENCE AS A WHOLE
Parallell vs. hierarchal processing
Hierarchal Processing, Complex Feature Detectors EXAMPLE IS V1-V5 PROCESSING
Detect simple to complex features: from lower to higher areas of the brain
Combine multiple inputs and fire only when they receive specific patterns
Paralell Processing
Many types of feature dictators process different aspects of environment in parallel
Color, brightness, texture, distance, movement are all being processed parallel to one anotheR: PRODUCES A UNIFIED PERCENT
How pathway + what pathway = unified percept of the world
WE USE BOTH
Problems with Bottom Up Processing
Inverse Projection Problem: problem of determining the object that caused a particular image on the retina when objects are creating the same image on the retina (
For example, an image of a circular disk could be produced by a flat disk viewed at an angle, or by a cylindrical object viewed head-on)
Impossible to solve using only bottom-up information ^^^^
Many argue that perception is more thna just patterns of neurons firing
Top-Down Processing
Begins with high level cognitiv processes, existing knowledge and prior expectations influence perceptions
Perception is impacted by factors beyond patterns of receptors firing
Formulate perceptual hypothesis
Examine features to check hypotheses
Recognize stimulus (MORE IMPORTANT THAN STEPS: RECOGNIZE THAT PAST EXPERIENCE CHANGES OUR INTERPRETATIONS)
Knowledge and experience can change how we experience and perceive objects
Bottom up processing may not be the whole story (loaf of bread location example)
Helmholtz, Theory of Unconcious Inference
Von Helmoltz proposed this theory to explain how we decide among the possibilities (recall the inverse projection problem)
We decide by making unconscious inferences about sensory inputs, OUR BRAIN FILLS IN THE UNKNOWN DETAILS without conscious awareness
Gestalt, Law of Continuity:
: when things are linked together, would make a straight or smoothly curved continious line are seen as belonging together
Law of similarity, Gestalt
Law of Similarity: group things that are similar together
Law of proximity
Law of Proximity: elements near one another tend to be perceived as belonging together
Law of closure
Law of Closure: tendency to clos edges or fill in gaps in an incomplete figure to make it more complete
Perceptual Constancy:
tendency to experience the same stable perception despite changes in sensory input; otherwise we’d have to rediscover what something is with change in lighting and distance
Context Effects:
surrounding environment impacts pervption; context in which something appears influences our expectations, which in turn impacts our perception
Likelihood Principle, Helmholtz
states that we perceive the object that is most likely to have caused the pattern of stimuli we have received; uses unconscious inference in which our perceptions are the result of unconcious assumptions that we make about the environment
The likelihood principle states that the visual system prefers the most likely interpretation of a stimulus, whereas the simplicity principle states that it prefers the most simple interpretation.
Speech Segmentation:
ability to tell where one word in a conversation ends and the next one begins
