Sensation
the activation of receptors in the various sense organs
Absolute Threshold
the smallest amount of energy needed for a person to consciously detect a stimulus 50 percent of the time it is present
Retina
final stop for light in the eye contains three layers: ganglion cells, bipolar cells, photoreceptors that respond to various light waves
Cones
visual sensory receptors found at the back of the retina; responsible for color vision and sharpness of vision
Difference threshold
the smallest difference between 2 stimuli that are detectable 50 percent of the time
Perception
the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion
Rods
visual sensory receptors found at the back of the retina; responsible for noncolor sensitivity to low levels of light
Opponent Process Theory (color)
theory of color vision that proposes four primary colors with cones arranged in pairs: red and green, blue, and yellow
Fovea
Very center of the retina where there are no rods, but there is a large concentration of cones.
Trichromatic theory
theory of color vision that proposes three types of cones: red, blue, and green
Cochlea
the snail-shaped structure of the inner ear that is filled with fluid
Perceptual constancy
refers to the tendency to perceive an object you are familiar with as having a constant shape, size, and brightness despite the stimuli changes that occur.
Monocular cues
(pictorial depth cues): cues for perceiving depth based on one eye only
Pheromones
Chemical signals released by organisms to communicate with other members of their species
Transduction
turning outside stimuli into neural activity
Weber's law
Whatever the difference between stimuli may be, it is always a constant.
Binocular Cues
cues for perceiving depth based on both eyes
Place theory
theory of pitch that states that different pitches are experienced by the stimulation of hair cells in different locations on the organ of Corti
Retinal disparity
differences between the images received by the left eye and the right eye as a result of viewing the world from slightly different angles; binocular depth cue, since the greater the difference between the two images, the nearer the object
Taste buds
taste receptor cells in the mouth; responsible for the sense of taste
Pitch
psychological experience of sound that corresponds to the frequency of the sound waves; higher frequencies are perceived as higher
Bottom-up processing
the analysis of the smaller features to build up to a complete perception
Feature detector
Cells that respond to specific features of a stimulus.
Gate control theory
pain signals must pass through a "gate" located in the spinal cord
Psychophysics
quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they produce
Sensory adaptation
the tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging
Signal detection theory
Your ability or likelihood to detect some stimulus is affected by the intensity of the stimulus (e.g., how loud a noise is) and your physical and psychological state (e.g., how alert you are).
Top-down processing
the use of preexisting knowledge to organize individual features into a unified whole
Accommodation (perceptual)
what occurs when new information or experiences cause you to modify your existing schemas. Rather than make the new information fit into an existing schema, you change the schema in order to accommodate the new information.
Frequency theory
theory of pitch that states that pitch is related to the speed of vibrations in the basilar membrane
Habituation
the tendency of the brain to stop attending to constant, unchanging information
Lens
another clear structure behind the iris, suspended by muscles; finishes the focusing process begun by the cornea
Optic nerve
Sends visual information to the brain.
Pupil
hole through which light from the visual image enters the interior of the eye
Vestibular sense
the sensations of movement, balance, and body position
Blindspot
the area in the retina where the axons of the three layers of retinal cells exit the eye to form the optic nerve; insensitive to light
Dark Adaptation
the recovery of the eye's sensitivity to visual stimuli in darkness after exposure to bright lights; night blindness
Iris
round muscle (the colored part of the eye) in which the pupil is located; can change the size of the pupil, letting more or less light into the eye; helps focus the image
Olfaction
Sense of smell
Convergence
the rotation of the two eyes in their sockets to focus on a single object, resulting in greater convergence for closer objects and lesser convergence if objects are distant
Hue
is determined by the length of the wave; long wavelengths are found at the red end of the visible spectrum (the portion of the whole spectrum of light that is visible to the human eye); shorter wavelengths are found at the blue end
Shape constancy
the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina
Size constancy
the tendency to interpret an object as always being the same actual size, regardless of its distance
Cornea
Clear membrane that covers the surface of the eye. Bends light waves so the image can be focused on the retina
Subliminal perception
the process by which subliminal stimuli act upon the unconscious mind, influencing behavior
Gustav Fechner
Expanded on Weber's work by studying absolute threshold
David Hubel
Demonstrated that neurons in the occipital lobe's visual cortex receive information from individual ganglion cells in the retina (feature detector cells)
Ernst Weber
Created Weber's law; worked with just noticeable difference/difference threshold.
Torsten Weisel
studied visual information processing and development in the US during the twentieth century. He performed multiple experiments on cats in which he sewed one of their eyes shut and monitored the response of the cat's visual system after opening the sutured eye.
Gibson
believed that perception is direct and meaningful