Visual perception Flashcards
Absolute threshold
minimum amount of stimulus energy required for our senses to perceive the stimulus in normal conditions
`Reception
stimulus energy is collected
Transduction
Stimulus energy is converted by receptors cells (rods and cones) into electrochemical nerve impulses
Transmission
receptor cells send impulses to primary sensory cortex
Selection
Selecting useful information and omitting useless information to prevent sensory overload
Organisation and interpretation
information reaches the brain where past experiences, motives values and context give the stimulus meaning
6 stages of vision
- Reception
- Transduction
- Transmission
- Selection
- Organisation
- Interpretation
3 biological factors that affect visual perception
Physiological makeup
Ageing
Genetics
How does physiological makeup affect visual perception?
If any structures or neural pathways are damaged
E.g. colour blindness is due to structural issues of the retina
How does ageing affect visual perception?
Maturing of our sensory perceptions
Examples of visual perception issues due to ageing
Presbyopia - lens loses flexibility which means it is difficult to see objects up close
Floaters - tiny clumps of matter that float in the vitreous fluid
Cataracts - eye lens start to become cloudy due to breakdown of protein
Glaucoma - affects optic nerve which causes disruption to transmission, thus leading to poor vision
Macular degeneration - build of grainy deposits in macula (centre of retina) which results in inflammation
How does genetics affect visual perception?
Inherited visual disorders can be passed down from parents to children
What is a psychological influence on visual perception?
perceptual set
What is a perceptual set?
A predisposition to see things the way they are according to certain preconceptions
4 factors that influence perceptual set
Past experience
Context - environment which stimulus is observed
Motivation - what we want to see (food instead of fuel if we are hungry)
Emotion - depending on how we feel ourselves
2 types of perceptual constancy
Size constancy
- even when the stimulus is further away we maintain the perception on the size of the stimulus
Shape constancy
- object maintains its shape despite changing the perspective its seen from
4 types of Gestalt principles
Figure-ground organisation
- where images are organised into being the central object of attention and a background. These are separated by an imaginary contour e.g. camouflage
Closure
- when we perceive an object as whole despite it being incomplete
Similarity
- elements that are similar to each other are grouped together
Proximity
- when parts of pattern are close together allowing those close together to be seen as a group
How can depth cues be classified?
Binocular depth cues
- using both eyes
Monocular depth cues
- one eye alone or both eyes together
2 aspects of binocular depth cues
Retinal disparity
Convergence
Retinal disparity
binocular depth cue
for objects within 6-7cm
when the brain compares and contrasts the 2 slightly different images because of the distance between the eyes
e.g. holding pen to your eye and focusing in and focusing away
Convergence
binocular depth cue
for objects within 6-7cm
as an object comes closer, our eyes come closer together to keep the object centred in our retina.
2 types of monocular depth cues
Accommodation
Pictorial depth cues
Accommodation (depth cue)
Tension in ciliary muscles is received by brain to confirm location of object (greater the tension, closer the object)
Pictorial depth cue
To create 3D perception of something 2D
5 types of Pictorial Depth Cues
- Linear perspective
- parallel lines are made to converge as they extend along the page
- Interposition
- basically overlap (which object is closer) - Texture gradient
- made to make surfaces appear to recede into the distance(blur)
- Relative size
- Object that is producing the largest retinal image is closer - Height in the visual field
- portraying objects farther away as being closer to the horizon
Social influence on visual perception
through formal education, people are able to learn how to interpret images relevant to their culture and society
Ponzo illusion
Uses linear perspective and height in the visual field to make it seem like the more distant line is the longest
Muller Lyer illusion
Arrowheads
Carpentered world hypothesis
Perceptual compromise theory
Carpentered world hypothesis
we make 3D forms of each figure using familiar features of buildings to do so
This causes the arrow-headed line as the leading vertical edge of a building’s outside wall and thus closer to the observer
The feather tails is perceived as being further away due to
Perceptual compromise theory
AIms to explain the Muller Lyer illusion
States that ‘closure’ is the reason (Gestalt principle) - we connect the bottom lines with the top lines - thus making the feather tailed seem longer since it has a longer connection
How does the Ames room illusion work?
The ceiling is not parallel to the floor - it slopes upward
Observer maintains shape constancy which sees the person moving in a straight line rather than towards the back of the room
Size constancy is prevented due to the use of monocular depth cues
Thus, room-size constancy is used which means the room looks the same size but the person appears to grow rapidly in size
