Visual Perception Flashcards
Where are the cones and rods located?
They are visual receptor cells located in the retina
What is a cone?
Responsible for colour and detail perception and is located in the fovea
What is a rod?
Responsible for vision in dim light and is located in the periphery
Where do the cones send their input?
To retinal ganglion cells
What is reception?
The absorption of physical energy
What is transduction?
Physical energy is converted into an electrochemical pattern in the neuron’s
What is coding?
One to one correspondence between aspects of the physical stimulus and aspects of the resultant nervous system activity ?
What are the 3 steps involved in from eye to cortex?
Reception to transduction to coding
What is the parvocellular pathway?
It is sensitive to colour and fine detail and most input comes from cones
What is the magnocelluar pathway?
Most sensitive to motion and most input comes from rods
How are the visual fields and hemispheres connected?
LVF -> RH
RVF -> LH
What are V1 & V2 responsible for?
Basic visual processing
What are V3 & V3A responsible for?
Form perception (especially moving stimuli)
What is V4 responsible for?
Colour perception and shape perception
What is V5 responsible for?
Motion perception
What is LOC responsible for?
Object perception
What are OFA and FFA responsible for?
Face perception
Given functional specialisation, how is visual information combined and integrated?
Binding visual features together
What is the binding-by-synchrony hypothesis?
Neurons that code difference dimensions start to oscillate in synchrony. It is unclear how and why such synchrony might occur and precise synchrony is implausible.
What is the ventral stream in the perception-action model?
‘What’ pathway, vision-for-perception, allocentric coding, sustained representation, usually conscious awareness and input from the fovea
What is the dorsal stream in the perception action model?
‘Where’ pathway, vision for action, egocentric coding, short-lived representations, usually unconscious
What is the Muller-Lyer illusion?
Both vertical lines are the same length however the arrows on the end are facing opposite directions.
What was the findings from Bruno from the Muller-Lyer illusion?
When pointing (using vision for action system) illusion size wa 5.5% however when verbalising a response (vision for perception), the illusion size was 22.4%.
What is the Ebbinghaus illusion?
Both centre circles are the same size but the one in the top figure looks larger than the one in the bottom.
When is the illusion larger?
With the vision for perception system than vision for action system.
Which stream does grasping objects require?
Requires both the ventral stream as well as the dorsal strea, when information from memory required to control grasping movements and conceptual knowledge needed to make most appropriate grapsing movement
What are the two dorsal systems?
Dorso-dorsal system and Ventro-dorsal system
What is the dorso-dorsal system?
Used to grasp objects rapidly
What is the ventro-dorsal system?
It uses memorised object knowledge to use objects appropriately
What is the intuitive approach?
Vision - perception - action
What is hue?
The colour itself e.g. distinguished red from yellow
What is brightness?
The perceived intensity of light.
What is saturation?
Allows us to determine whether a colour is vivid or pale - influenced by the amount of white present
What is colour constancy?
Perceived colour remains the same despite changes in the wavelengths in illuminant
What is chromatic adaption?
Sensitivity to illuminate of any given colour decreases over time
What is the retinex theory?
Observers compare light reflected from a surface against that reflected from adjacent surfaces
What are the 6 monocular cues?
Linear perspective, texture, interposition, familiar size, blur and motion parallax
What is linear perspective in relation to depth perception?
Based on laws of optics
What is texture in relation to depth perception?
Objects slanting away have a texture gradient
What is interposition in relation to depth perception?
Nearer objects hides part of a more distant one
What is familiar size in relation to depth perception
The distance of familiar objects is easier to judge than that of unfamiliar ones
What is motion parallax in relation to depth perception
Movement in one part of retinal image relative to another
What is stereopsis (binocular cue)?
It enhances depth perception and allows us to see the environment three-dimensionally. It is based on slight difference or disparity between the two retinal images. It is very powerful at short distances only and individuals with amblyopia (lazy eye) have impaired stereoscopic depth perception.
What is additivity?
Information from all cues is combined or integrated
What is selection?
Information from a single cue is used, with information from the other cues being ignored
What is perceived size proportional to?
Retinal size and perceived distance
What does subliminal perception involve?
Subjective measure and object measure
What is subjective measure?
Observers failure to report awareness of a stimulus
What is objective measure?
Observers ability to make accurate forced-choice decisions about a stimulus
