Module 1 Flashcards
Categories
Mental groupings or classifications we use to organise and make sense of the vast amount of sensory information we encounter. We place perceptual information into categories to help us to recognise and name objects.
Dorsal stream (where/how pathway, also called the ‘action’ pathway)
Processes information through the V3 area with increasing complexity (i.e. stimuli motion), which then projects to the V5/medial temporal visual area. The MT contributes to the perception of speed, eye movement and motion. From V5, information is projected to the posterior parietal cortex. This helps us identify where things are to prepare us to take action in response.
Ventral stream (also called the ‘what’ pathway)
Information is processed further through V3 with increasing complexity (orientation, colour, curvature processing). From V3, the information is projected to V4 where further processing occurs (further processing complexity e.g. simple shapes). This information is then projected to the inferior temporal cortex where complex shape and object recognition occurs.
Prosopagnosia
A type of visual agnosia where an individual is unable to perceive faces. Caused by damage to the fusiform face area.
Can be acquired as a byproduct of damage to the brain.
Can also be congenital, meaning people can be born with it and it can run within families.
Subtractive Colour Mixing
When mixing colours together causes fewer wavelengths to be reflected into the eye. The more colours are mixed (i.e. paints), the darker the colour, as the host material absorbs more light and reflects less into the eye. The colour is being ‘subtracted’. The reference percentage is reduced closer to black.
Cyan, yellow, magenta
E.g. Paints on canvas
Additive Colour Mixing
When mixing colours together causes more wavelengths to be reflected into the eye- the colour is ‘added’. Aka the reflectance percentage is being increased closer to white.
Red, blue, green.
E.g. smart phone, monitors
Brightness
Determines how light or dark the colour is. Lower brightness gives a darker colour, including black at 0% brightness. Higher brightness gives a lighter colour, including white at 100% brightness.
Centre-Surround Receptive Field
Receptive field- the retinal region over which a cell in the visual system can be influenced (excited or inhibited) by light.
The area of a nerve fibre that causes the neuron to fire. A neuron’s receptive field covers a much greater area than a single photoreceptor, rather it covers hundred-thousands of receptors.
In a centre-surround receptive field, the area in the “centre” of the receptive field responds differently to light than the area in the “surround” of the receptive field. This allows us to capture differences in stimuli such as contrasts and edges in the environment.
‘ON’-centre cell
Presenting light to the centre increases firing to bipolar cells (excitatory area), while stimulation of the surround causes a decrease in firing (inhibitory area). Results in enhanced contrast between light hitting the two areas.
‘OFF’-centre cell
Presenting light to the centre decreases firing to bipolar cells (inhibitory area), while stimulation of the surround increases firing (excitatory area).
Trichromatic theory of colour vision
The theory that posits there are three types of cones found in the fovea in the retina, each maximally absorbing light at a particular wavelength allowing us to see all combinations of colours.
Opponent-process theory
Colour vision is caused by opposition physiological responses generated by blue/yellow, red/green.
Opponent retinal ganglia cells exist for red-green and blue-yellow. These cells have an on-centre/off-surround configuration or vice versa. E.g. a red on-centre cell excites when red light hits its centre but will have an inhibitory response to green light in its surround.
Red-green colour blindness
Deuteranopia or Protanopia. Unable to distinguish between red and green hues. Most common form of colour blindness, usually affecting males.
Blue-yellow colour blindness
Tritanopia. Individuals are unable to distinguish between blue and yellow hues. To perceive yellow, M-cone and L-cone activation are needed. The absence of the S-cone means there is no information to tell the brain the ratio of S-cone to M & L-cone activation needed to perceive yellow.
Colour Constancy
The perceptual ability to view colours as consistent, across different types of illuminations.
Also helps to perceive whole objects as the same colour. An example of top-down processing.
Principle of Pragnanz (Good figure)
Every stimuli is perceived in the simplest way possible. E.g. perceiving the Olympic rings as five circles instead of nine overlapping shapes.
Principle of Good continuation
The tendency to perceive lines or curves that are connected and following an established direction as being grouped together. When there is an intersection between objects, we differentiate objects separately.
Figure-Ground Segregation
- The figure is more “thing like”, memorable, and is perceived as being in front of the ground
- The ground is more uniform and less memorable than the figure
- The border ownership separates the figure from the ground. The border is perceived as belonging to the figure
Physical regularities
Regularly occurring physical properties of the environment. E.g. vertical and horizontal lines, the light-from-above assumption
Semantic regularities/Scene Schema
Using our knowledge of scenes and context to quickly anticipate what would happen within them.
The characteristics associated with activities that are common in different types of scenes.
The knowledge of what a given scene typically contains is called a scene schema.
Bayesian Inference
Our perceptions are based on our prior probabilities (the initial probability of an outcome) and the extent to which available information is consistent with an outcome (the likelihood of an outcome) to create a perceptual ‘conclusion’. E.g. colds and heartburn are common, lung disease is not (priors). A bad cough is a symptom of a cold or lung disease, not heartburn (additional). Therefore, a cold is most likely causing the cough (conclusion).
Relative Height
Objects with their bases closer to the horizon are usually seen as further away. 2D images: objects lower in the field of view are perceived as closer, objects higher in the field of view are perceives as being further away.
Relative Size
When comparing unfamiliar objects to each other, the object that produces a smaller image on the retina is perceived as further away. Without a reference we assume that objects are the same size.
Linear perspective
Related to relative size. E.g. looking at a railroad track where two parallel lines converge on a vanishing point, we experience a sense of depth because we assume the width of the track is the same throughout. The size on our retina is smaller for the background than the foreground, creating depth perception.
