Visual Perception Flashcards
Sensation
An automatic physical process that happens in the sense organs. It is the same in everyone.
Three stages: Reception, Transduction and Transmission.
Perception
A psychological process that gives meaning to the stimuli detected by sense organs. 3 Stages; Selection, Organisation and Interpretation
Cornea
Dome shaped outer covering of the eye.
Pupil
Black hole in the centre of the eye.
Lens
Clear layer behind the pupil.
Retina
The part that absorbs the light.
Rods
Found in edges of retina and allow us to see in dim light. Photoreceptor.
Cones
Found in centre of retina and allow us to see in bright light, colour and detail. Photoreceptor.
Optic Nerve
Nerve that connects the eye to the brain.
Blind spot
Back of the retina where the optic nerve connects to the eye.
Fovea
A small divot next to the blind spot where retina is thin. High density of rods.
Sensation Stage 1 - Reception
When the stimulus is detected by sensory receptor cells located in our sense organs.
Sensation Stage 2 - Transduction
Where sensory receptors convert stimulus energy into electrochemical energy.
Sensation Stage 3 - Transmission
Where electrochemical impulses are sent along the neural pathways to the brain.
Perception Stage 1 - Selection
Where feature detector cells filter the impulses by choosing some for further processing and ignoring others.
Perception Stage 2 - Organisation
Refers to the reassembling of features of sensory stimuli to form a whole or pattern that can be given meaning.
Perception Stage 3 - Interpretation
Where the brain gives meaning to stimuli so we understand what they represent about the world.
Top-down processing
The process of applying prior knowledge and expectations to sensory infomation.
Bottom-up Processing
The processing of sensory information beginning with the small details to form the big picture.
Depth Perception
The ability to see 3D space and to accurately judge distance.
Binocular Cues
Depth cues that rely on information from both eyes.
Retinal Disparity and Convergence.
Retinal Disparity
Binocular depth cue created by small differences between the retinal image in each eye.
Convergence
Binocular depth cue that involves the brain detecting the movement in the muscles surrounding the eyes.
Monocular Depth Cues
Cues that rely on information from only one eye.
Accommodation and Pictorial Depth cues.
Accommodation
Monocular depth cue involving the stretching of the lens when focusing on distant object and bulges when focusing on close objects.
Pictorial Cues
Monocular Cues present in 2D images that allow the brain to see it as 3D.
Linear perspective, Relative size, Interposition, Texture gradient and Height in the visual field.
Pictorial Cue 1: Linear Perspective
Where the apparent convergence of parallel lines creates the illusion of increasing distance.
The (___) at X and Y form parallel lines. They appear to be converging towards Z.
Therefore, we perceive X and Y to be closer than Z.
Pictorial Cue 2: Relative Size
Where the smaller retinal image is perceived as being further away.
The (___) at point X casts a larger retinal image than the
(___) at point Y. Therefore, we perceive the (___) at point X
to be closer than the (___) at point Y.
Pictorial Cue 3: Interposition
Where one object partially blocks another and is perceived as being in front of the other.
(___) at X is blocking (___) at Y. Therefore, we perceive (___) at X to be in front of, and
closer than, (___) at Y.
Pictorial Cue 4: Texture Gradient
Where features become smaller and less detailed the more distant an object becomes.
(___) at X have highly detailed
surface features compared to (___) at Y. Therefore, we perceive (___) at X to be closer than (___)at Y.
Pictorial Cue 5: Height in the Visual Field:
Where objects located closer to the horizon appear further away.
(___) at X is closer to the horizon than (___) at Y. Therefore, we
perceive (___) at X to be further away than (___) at Y.
Gestalt Principles:
Explains how we interpret visual information by grouping elements to see a whole.
Figure ground, Closure, Similarity and Proximity
Gestalt Principle 1: Figure Ground
The tendency to perceive the figure as more relevant.
The (figure) in the foreground of the picture is seen as significantly more prominent than the (ground). We therefore separate the figure of (figure) from the (ground) which surrounds it and perceive the (figure) as more significant.
Gestalt Principle 2: Closure
Tendency to perceptually complete an incomplete object.
When we look at the (incomplete object), we see a distinct space between the (say what there are spaces between). As a result, we mentally close
the gaps to perceive it as (the object).
Gestalt Principle 3: Similarity
Viewer’s tendency to perceive stimuli that have similar visual features as a group.
When we look at the collection of (similar items), we recognize that they are alike in shape and form. As such, we mentally group them together and perceive them to be (say what we see them as).
Gestalt Principle 4: Proximity
Where stimuli that are close together are perceived as belonging to one unit.
When we look at the (say what is close together), we recognize that they are close to one another. As such, we mentally group them together and perceive them to be (say how we see them).
Visual Constancies
Tendency to perceive the visual stimulus as remaining constant. Size, Shape and Orientation Constancy.
Size Constancy
Perceived size remains the same, despite changes in retinal image.
Shape Constancy
The perceived shape remains the same, despite changes in the retinal image.
Orientation Constancy
Perceived orientation remains the same despite changes in the retinal image.
Context
Refers to information that surrounds a stimulus that influences the perception.
Motivation
A person’s desires can influence perception.
Cultural Influence on Vision
Cultural upbringing can cause differences in perception
Visual Illusions
Consistent perceptual errors in the interpretation of a visual stimulus
The Ponzo Illusion
This optical illusion involves two identical lines placed over a pair of converging lines or railway tracks. The line placed higher on the converging lines appears longer than the one placed lower, even though they are the same length.
The Ames Room Illusion
An Ames Room appears to be a rectangular-shaped room, but it’s trapezoidal. When viewed from a specific angle through a peephole or a camera lens, it creates the illusion that people standing in one corner of the room are significantly larger or smaller than those standing in the opposite corner.
Muller - Lyer Illusion
Two lines, one with arrows pointing inward, the other pointing outward. Inward arrows are perceived to be longer.
Carpentered World Hypothesis
Western buildings typically have lots of right angles so Western people are more likely to fall into this illusion.
Apparent Distance Theory
If two objects cast the same-sized retinal image, but one is perceived to be further away, our brain interprets the more distant object as being further away.
Agnosia
Loss or impairment of the ability to identify objects, people or sounds using one sense.
Caused by Dementia, Trauma or Environmental Concerns.
Visual Agnosia
Where the sufferer has a total or partial loss of the ability to identify similar objects.
Prosopagnosia
Cannot see faces, only see little details but not the whole face.
Synaesthesia
A perceptual anomaly where the reaction from one sense can cause another.
Grapheme
Colour Synaesthesia
