Perception Flashcards
Briefly describe the visual pathway.
Eye -> Retina -> LGN -> Primary visual cortex
What are ‘simple’ cells in V1 selective for?
Position on retina, orientation of edge/bar and size/width of bar.
What are ‘complex ‘ cells in V1 selective for (in addition to ‘simple’ cell sensitivity)?
Movement within the receptive field.
What are ‘complex ‘ cells in V1 selective for (in addition to ‘simple’ cell sensitivity)?
The length of the edge or bar - Must stop at one/both ends.
How does V1 detect so many different shapes?
There are many different receptive fields, with different orientation, spatial scales and positions.
What leads to a local virus defect?
Damage to V1.
How is the V1 mapped?
On the cortex, with areas processing contours on particular regions of the retina.
What is the catchphrase for Gestalt psychology?
“The whole is more than the sum of the parts.”
Give the 5 Gestalt ‘grouping principles.’
Similarity, proximity, closure, good continuation and common fate.
Which cells are selective for edges defined by good continuity and closure?
V2 cells
Which ‘grouping principles’ are impaired by V2 damage?
Good continuity, closure and similarity (particularly colour).
Give 6 examples of things which change an object’s image.
Distance, position, perspective view, orientation, lighting and occlusion of parts.
Describe object agnosia.
The failure to recognise without any loss of intelligence or vision.
Describe Marr’s model of recognition.
Edge filters use Gestalt grouping to separate segments and arrange them as cylinders to match 3D memorised models.
Suggest a problem with Marr’s model of recognition.
Many objects are hard to recognise if upside down or rotated.
Describe Biederman’s ‘Recognition by Components.’
Geon types and arrangement for each part of an object are determined and matched to a memorised description.
Describe a problem with Biederman’s ‘Recognition by Components.’
It does not differentiate objects within classes.
What do cells in the temporal cortex code for?
Shape, colour and texture.
What can cause object agnosia?
Lesion of the temporal cortex.
What is prosopagnosia?
Face agnosia, where individuals may recognise objects but cannot recognise individual faces.
When does the right fusiform area become active?
When shown faces.
When does the right occipitotemporal area become active?
When shown bodies.
How do hypothetical Grandmother cells work?
They respond to one object only.
(External/internal) features are more important for recognising unfamiliar faces.
External
(External/internal) features are more important for recognising familiar faces.
Internal
What does improved recognition of caricatures imply?
Faces are coded by their difference from average.
What 6 basic emotions have universal interpretations?
Happiness, sadness, anger, fear, surprise and disgust.
How do patients lacking the amygdala fail to reconfigure fear expressions?
They do not look at the eyes.
What brain area is activated by expressions of disgust?
Insula cortex
Which brain area is sensitive to both attractiveness and gaze direction?
Ventral thalamus
Which brain area has increased activity based on smiling?
Orbito-frontal cortex
What are some explanations for colour after effects?
Pigment bleaching, neuronal fatigue and opponent processing of colour.
What explains brightness and colour contrast?
They are coded relative to the surround.
What explains motion contrast?
Stationary objects appear to move in the opposite direction to moving ones.
What is the Zöllner illusion?
Orientation contrast
Briefly describe the stages of bottom-up processing.
Low level feature detectors -> Mid level pattern detectors -> High level object detectors
Briefly describe the stages of top-down processing.
Memorised concepts -> High level object detectors -> Mid level patter man detectors
What is the word superiority effect?
Detecting a letter is easier in the context of a word.
What causes a ‘target present’ bias in a signal detection test?
When there is a reward for hits but no penalty for false alarms.
What causes a ‘target absent’ bias in a signal detection test?
When there is no reward for hits but a sever penalty for false alarms.
Give 4 factors that influence the attractiveness of a face.
Averageness, symmetry, sexual dimorphism and health.
Give 3 factors that influence someone feeling attraction to a face.
Hormone levels, status and imprinting.
Describe Gibson’s theory of direct perception.
Visual information directly controls actions so that visual properties of objects ‘afford’ actions.
What is ataxia?
Ability to recognise objects but not guide actions.
When do mirror neurones discharge?
During execution, observation and sound of an action, and even when it can only be deduced.
What is the motor theory of speech?
We simulate production of speech we hear.
