Vision Flashcards
What is Visual Reception?
The sensory stimuli received by visual sensory receptors is light. Light comes in the form of electromagnetic energy (as waves across space). The human eye can detect light on the visible light spectrum from 350-750 nanometres.
Light travels through the eye, to the photoreceptor cells on the retina. There are two kinds of photoreceptors: rods and cones. Rods work to detect images in low levels of light and do not allow us to see colour, whereas cones work to detect images in well-lit conditions and are able to pick up on small details and colour.
What is Visual Transduction?
The rods and cones are responsible for the transduction of electromagnetic light energy into electrochemical energy, which is a form that can be sent to the brain for processing.
What is Visual Transmission?
The visual sensory message is sent to the brain via the optic nerve and then the thalamus for processing.
What are the parts of the eye? What do they do?
Cornea (A curved transparent covering of the eye. Allows light in and protects the front of the eye.)
Pupil (Is the opening within the iris through which light enters the eye.)
Lens (The structure of the eye that helps to focus light from the external environment onto the retina.)
Ciliary Muscles (Allows the eye to move.)
Retina (A layer of specialised neurons that line the rear inner surface of the eye. It receives and absorbs light, processes images and transmits neural messages to the visual cortex of the brain.)
Sclera (The thick, tough, outer covering of the eyeball.)
Vitreous Humour (The jelly-like structure of the eye that nourishes and supports the retina and helps form the shape of the eyeball.)
Aqueous Humour (It helps the cornea maintain its curved shape.)
Blind Spot (A small region of the retina, where the optic nerve leaves the eye, which is insensitive to light.
Optic Nerve (Carries information from the retina to the Occipital Lobe.)
Rods (Specialised receptors in the retina of the eye which functions most effectively in low levels of illumination and is important to night vision and peripheral vision.)
Cones (Specialised photoreceptors in the retina of the eye that functions most effectively in well-lit conditions and has important roles in visual acuity and colour vision.)
Tapetum (The colourful shiny material located behind the retina. Found in animals with good night vision. It reflects light back through the retina.)
What are the 5 Gestalt Principles?
Camouflage (Blends into the background)
Figure-Ground (This principle involves our tendency to see some figures as being at the front of an image, i.e. the ‘foreground’, and others as falling back into the ‘background’)
Closure (When we perceive an object as a whole despite it being incomplete)
Similarity (Group together to provide a ‘whole’ single unit)
Proximity (Individual parts are close to each other we tend to perceive them as ‘whole’)
What are the Visual Constancies?
Size Constancy - Refers to the fact that we maintain a constant perception of an object’s size even if the object moves nearer or further away.
Shape Constancy – Refers to the fact that we can
interpret objects when viewed from any angle.
Depth Perception - What are Binocular Depth Cues?
Retinal Disparity - Example; (Hold a pen at arm’s length and look past it to the other side of the room. Close one eye and then the other and watch how far the pen ‘jumps’ from side to side. Now bring the pen closer – about 40cm from your nose and repeat the process.)
Convergence - Example; (Hold your pen vertically at arm’s length and slowly bring it closer to your nose, watching it with both eyes all the time. As the pen gets closer to your nose, you can feel your eyes turning and soon you go ‘cross eyed’.)
What are the Monocular Depth Cues?
Accommodation (Accommodation involves the lens of the eye changing shape so that it can focus light rays onto the retina.) Example; (Take a pen and close one eye, move the pen as close to as you can while maintaining focus – do this until you feel the tension in your eye.)
What are the Pictorial Depth Cues?
Linear Perspective Interposition Texture Gradient Relative Size Height in the Visual Field
What is a Perceptual Set?
A predisposition to perceive stimuli in a certain way.
