Lecture 3 Flashcards
Perception
Organisation, identification and interpretation of sensory information
-how we interpret info affects how we interact with the world
Bottom up pathway
Perceptions are built from sensory input
-feed forward
-Receives info from what/where pathways
Top-down processing
Interpretation of sensations are influences by available knowledge, experiences and thoughts
-regions at end of what/where pathways move to V1
Factors affecting perception (8)
- Sensory adaption
—not perceiving stimuli that remains relatively constant over prolonged periods of time - Motivation
- Attention
—concentration on specific parts of our environment (often at the exclusion of others) - Beliefs/values/prejudices/expectations
- Inattentional blindness
—failure to notice something completely visible because of lack of attention - Change blindness
- Colour perception
- Life/cultural bias
Retina
Internal surface of eye that contains photoreceptors that convert light into neural signals
-Relayed to the brain via optic nerve
Blind spot
Point at which optic nerve leaves the eye
-no rods or cones are present here
Rods
Specialised for level of low light intensity
-located primarily in periphery
Cones
Specialized for levels of high light intensity and detection
-packed more densely in center of retina (fovea)
Transduction of light
- Light enters though cornea
- Passes through pupil
- Refracted through the lens
- Focused on retina tissue at back of eye
- Captured by photoreceptors in fovea and converted into neural signals
- Neural signal transmitted to brain through optic nerve
Primary visual cortex (V1
Area at back of brain responsible for early processing of visual signals (how light something is, color, movement, etc)
-signals travel to here via processing station called lateral geniculate nucleus
-V1 cells respond to light into particular orientations, lengths, etc.
Dorsal pathway
“Where” pathway
Ventral pathway
“What” pathway
Word superiority effect
Easier to identify a letter if it appears in a word rather than alone or in a non-word
V4
Region associated with color perception
-acheomatopsia is the failure to perceive color
V5
Region associated with motion perception
-akinestopsia is the failure to perceive visual motion
Stages of object recognition
- Initial stage
-detection of basic visual elements (colors, edges, etc) - Intermediate stage
-grouping basic elements into higher units that code depth cues and segregate surfaces into figure and ground - Advanced/final stage
-recognising the object and attributing meaning to it
Feature detection
Detecting patterns on the basis of their features or properties
Slefridges pandemonium model (3 levels)
- Features
-property of stimulus (color, shape, size) - Cognitive demons
-decides whether stimulus matches its particular patterns - Decision demons
Decides which pattern is being recognized based on cog demon input
Recognition by components
Decomposing objects into fundamental 3D geometric shapes and comparing with existing memory representations
-explains why we can recognize objects from different viewpoints
Gestalt grouping principles
Perception is holistic rather than atomistic
-grouping of visual features to form a whole
-follows certain organisational principles
Template matching
Comparing configuration of current sensory input with standard configuration we have
-we have a prototype/template
Apperception agnosia
Failure to understand meaning of objects
-deficit at level of object perception
Associative agnosia
Failure to understand meaning of objects
-deficit at level of semantic memory
Integrative agnosia
Failure to integrate parts into wholes
Fusiform face area
Area in temporal lobes that responds more to faces than other visual objects
Face recognition units
-stored knowledge of the 3D structure of similar faces
Person identity nodes
-abstract description of people that links perceptual knowledge with semantic knowledge
Propoagnosia
Impairments of face processing
-do not reflect difficulties in early visual analysis
Modality appropriateness hypothesis
Different senses are better at processing different stimuli
-depending on situation, different sensory modalities will dominate
Visual prepotency effect
Visual system dominate when it comes to perceptual processing
-conflict resolution
—when visual and auditory info conflict, we often rely more on visual info to resolve this conflict
Visual agnosia
Unable to identify objects but still able to act upon them
-result of damage to ventral stream
Optic ataxia
Unable to properly grip when acting upon objects but still able to identify the object
-result of damage to Doral stream
Attention
Processes that allow us to select info for further processing
-selection based on relevance to importance to current goals
Information processing
Idea that world contains info for humans to process
Information theory
A message is inversely related to its probability of occurrence
-less likely it is, the more info it conveys
—framework for understanding decision making, memory storage, and communication
Alertness and arousal
Most basic level of attention
Selective attention
Involves selection of info essential to task
—cocktail party effect
—dochotic listening
Divided attention
Extending to more than one thing at a time
-we can do more than one task, but as they become more complex they interfere with each other
—structural limits
—central bottleneck (not actually completely at same time, but switching between)
Sustained attention
Focusing on a single task for prolonged period of time
—vigilance (externally imposed sustained attention example: your job)
Automaticity (processing without attention)
Fast and effortless processing that requires little to no focused attention
-tasks that first require controlled processing can become automatic
spatial attention
Spotlight may move from one place to another or move in and out
-location of attention not necessarily same as eye fixation
Exogenous orienting/shuft
Attention externally guided by a stimulus
-Bottom-up
-attention is captured
Endogenous orienting/shift
Attention guided by the goals of perceiver
-top-down
Non-spatial attention
Object based attention
—different parts of visual ventral stream increase in activity when attended
Attentional blink
Inability to report a target stimulus if it appears too soon after another target stimulus
Neglect
A failure to attend to stimuli on opposite side of space to a brain lesion
-may only eat from half of plate, read half of page, bump into objects on that side
Coates’s delusion
Thinking one is dead
Capgras delusion
Thinking loved ones are imposters
Reduplicative paramnesia
Belief in the existence of duplicate persons, places, body parts, etc
