Sensation
Process of detecting a physical stimulus, such as light, sound, heat, or pressure.
Perception
Process by which we organize or make sense of our sensory impressions.
Absolute Threshold
The smallest possible strength of a stimulus that can be detected half the time.
Cornea
Protects the eye and helps gather and direct light rays.
Iris
A colored muscle that controls how much light enters the pupil.
Lens
Bends light and focuses in onto the retina.
Retina
Contains light sensitive photoreceptor cells.
Fovea
The part of the retinal stimulated by light when you look directly at something. Contains most of the cones.
Blind Spot
Contains no rods or cones. Also called the optic disk.
Optic Nerve
Sends signals originating in the photoreceptor cells to the brain.
Occipital Lobe
The part of the brain that converts signals from the optic nerve into an image.
Rods
Sensitive only to the intensity of light. Distributed more densely as you approach the lends. 125 million.
Cones
Detect color. Located primarily in the fovea. About 7 million.
Trichromatic Theory
Says that some cones are especially sensitive to red light (long wavelengths), some to green light (medium wavelengths), and some to blue light (short wavelengths). This explains red-green color blindness.
Opponent Process Theory
Says that opposing pairs of color receptors respond to red or green, blue or yellow, and black or white. This explains afterimages.
Ear Canal
Collects sound waves.
Eardrum (Tympanic Membrane)
Vibrates in response to sound waves.
Ossicles (Hammer, Anvil, Stirrup)
The three bones of the middle ear. Amplify the sound wave vibrations.
Semicircular Canal
Detect our position in space; sense of balance.
Cochlea
Contains the basilar membrane and hair like receptor cells known as cilia.
Auditory Nerve
Sends signals originating in the cilia to the brain.
Temporal Lobe
The part of the brain that converts signals from the auditory nerve into a sound.
Frequency Theory
Says that the brain interprets pitch by the frequency of neural impulses sent to the brain. Best explains discrimination of low pitch sounds.
Place Theory
Says that the brain interprets pitch by the section of the basilar membrane that is stimulated by sound waves. Best explains our discrimination of high-pitch sounds.
Law of Figure Ground Perception
The tendency to perceive geometric forms against a background.
Law of Closure
The tendency to fill in the gaps, resulting in the perception of a broken figure as being complete or whole.
Law of Similarity
The tendency to perceive objects of a smaller size, shape, or color as belonging together.
Law of Good Continuation
The tendency to group elements that appear to follow in the same direction together as a single unit or figure.
Law of Proximity
The tendency to group together objects that are near one another.
Principle of Relative Size
It two or more objects are assumed to be similar in size, the one that appears larger is perceived as being closer.
Principle of Texture Gradient
Distance objects appear to have less clearly -defined detail than closer objects.
Principle of Linear Perspective
Parallel lines appear to come closer together as distance increases.
Shadowing
Shadows and highlights can serve as depth cues.
Overlap
Objects which partially block the view of other objects are perceived as being closer to us.
Motion Parallax
When we are moving, objects seem to move forward with us (ex: the sun) are perceived as very distant. When objects seem to move away from us, they are perceived as being closer.
Convergence
In order to maintain focus on an object moving closer to us, we must cross our eyes a little. Resulting tension is a depth perception cue.
Binocular Disparity
The objects present very different images on our two retinas, we perceive these objects as close. As distance increases, the two images become more similar.
Perception of Movement 1
If you are stationary then objects that you know are not moving will appear stable. If these non-moving objects appear to move or change in appearance, then this is a cue that you must be moving.
Perception of Movement 2
The body gives off certain internal cues, which tell you that you're moving (unsteady feeling).