Below is a list of vocabulary words in order by content.

Absolute Threshold:

a statistically determined value that refers to a point at which a stimulus is detected 50% of the time.

Difference Threshold:

minimum change in stimulation required for a change in detection to be noticed.

Weber's Law:

called the first quantitative law of psychology; relates changes in perception to stimulus magnitude.

Signal Detection Theory:

view that is based on the subject's ability to detect a stimulus against an environmental background of noise.

Receiver Operating Characteristics:

individual decisional factors that affect thresholds.

Subliminal Perception:

perception that occurs below some threshold point where the stimulus events are not obvious.

Receptors:

cells that detect different forms of energy and convery it into the electrochemical signals used by the nervous system.

Sensory Adaption:

decline in receptor activity elicited by an unchanging stimulus that results in a loss of sensitivity.

Habituation:

decline in the response elicited by repeated stimulation, not due simply to adaption.

Visible Spectrum:

band of electromagnetic radtiation we see, ranging between 390 and 760 nanometers.

Cornea:

clear membrane that lies in front of the lens.

Iris:

colored part of the eye that controls the amount of light reaching the retina by expanding or contracting in size.

Pupil:

opening in the center of the iris.

Lens:

translucent structure that lies behind the pupil and changes shape to focus an image.

Retina:

tissue that lines the back of the eye and contains the photoreceptors.

Accomidation:

change in the lens used to maintain a focused image, particularly when the image is presented close up.

Convergence:

moving the eyes inward to look at a nearby object.

Rods:

photoreceptors used for colorless vision in dim light.

Cones:

photoreceptors used for color vision in well-li conditions.

Bipolar Cells:

specialized cells that connect rods and cones to ganglion cells.

Ganglion Cells:

carry the visual information from the bipolar cells to the brain.

Optic Nerve:

Crainial nerve exiting from the back of the eye that is formed from the axons of the ganglion cells.

Blind Spot:

region of the retina that has no receptors where the optic nerve exits the eye.

Summation:

occurs when a single ganglion cell connects with many bipolar cells, resulting in a smaller optic nerve.

Visual Acuity:

ability to make fine visual discriminations between and among objects in the visual environment.

Fovea:

small, cone-rich area of the retina that supports high acuity.

Hue:

psychological dimension of color related to wavelength; different hues correspond to different colors.

Brightness:

psychological dimension of color related to amplitude.

Saturation:

Psychological dimension of color related to the complexity of the waveform, or how many wavelengths are in a given light source.

Young-Hemholtz Color theory or Thichromatic Color Theory:

proposes color is determined by the relative activity in red-, blue-, or green-sensitive cones.

Additive Color:

mixture based on the addition of wavelengths.

Subtractive Color:

mixture based on the subtraction of wavelengths.

Oppenent-Process Color Theory:

proposes that color information is organized into three antagonistic pairs.

Monochromacy:

condition that results when people have absolutly no color vision.

Dichromacy:

condition that results when a person has some color vision, but cannot see red and green, or blue and yellow.

Dark Adaption:

increased visual sensitivity that occurs in a dark environment.

Light Adaption:

reduction in visual sensitivity that occurs when you enter a light environment.

Visual Cortex:

the part of the occipital lobe located at the back of the brain that receives visual information.

Optic Chiasm:

point at which the optic nerves from each eye join, cross over, and project to the opposite side of the brain.

Receptive Field:

the region of the retina that, when stimulated, affects the cell.

Simple Cells:

cortical cells in the visual cortex that respond to a line of light presented in a particular orientation, or to a small spot of light.

Complex Cells:

cortical cells in the visual cortex that react to a bar moving in a particular direction.

Hyperomplex Cells:

cortical cells in the visual cortex that respond to a moving bar of particular length.

Feature Detectors:

cortical cells in the visual cortex that respond to specific stimulus patterns.

Dyslexia:

impairment in the visual cortex that leads to difficulty in learning to read, write, or spell.

Sound Waves:

changes in air pressure that produce sound.

Frequency:

rate at which the waveform expands and contracts; measured in hertz (Hz).

Pitch:

psychological dimension of sound related primarily to frequency.

Loudness:

psychological dimension of sound tied to amplitude but also affected by frequncy.

Timbre:

psychological dimension of sound related to the complexity of the waveform.

Harmonics:

sounds that are multiples of the fundamental frequency.

Tympanic Membrane:

membrane of the ear that detects changes in air pressure; commonly referred to as the eardrum.

Ossicles:

bones in the middle ear that transmit vibrations from the eardrum to the cochlea.

Cochlea:

fluid filled coil that contains the hair cells.

Basilar Membrane:

membrane of the cochlea that supports the hair cells.

Hair Cells:

receptors for hearing.

Tectorial Membrane:

membrane that lies over the hair cells.

Auditory Nerve:

cranial nerve that carries auditory information from the hair cells to the cortex in the brain.

Auditory Cortex:

region of the temporal lobe of the brain that receives auditory (hearing) information.

Place Theory:

relates perceived pitch to the region or place along the basilar membrane that is activated by a particular auditory stimulus.

Bekesy's Theory:

version of the place theory that ties pitch to the form of a traveling wave.

Frequency Theory:

relates perceived pitch to the frequency of incoming sound waves and the frequency of firing in the auditory nerve.

Volley Principle:

a cluster of neurons may share in the coding of higher frequencies.

Conductive Deafness:

loss of hearing due to a problem in conducting air vibrations to the cochlea.

Perceptive Deafness:

hearing loss caused by a problem in the hair cells, auditory nerve, or cortical neurons.

Taste Buds:

cluster of receptors located on the tongue that determine different tastes, such as sweet and sour.

Taste Cells:

individual taste receptors located on the taste buds.

Pheromones:

odors used for communication by animals.

Olfactory Cells:

receptor cells located in the olfactory epithelium that are responsible for smell.

Trigeminal Sense:

chemoreceptor system in the nose that is responsive to certain food flavors.

Ansomia:

inability to detect odors.

Somesthetic Perception:

perception of the skin senses such as cold or pain, and also bodily position.

Epidermis:

outermost of the three layers of skin, composed of dead cells.

Dermis:

middle layer of the three layers of skin, composed of living cells.

Subcutaneous Tissue:

inner layer of the three layers of skin.

Specificity Theory:

each sensation is coded by the activity in a particular kind of receptor.

Pattern Theory:

sensations are coded by the pattern of activity in a group of receptors.

Visual Substitution System (VSS):

a matrix of vibrating pins used to convey visual information to the skin.

Gate Control Theory:

proposes pain is modulated by a spinal gate that determines whether a pain signal is allowed to go on to the brain.

Kinesthetic System:

the system that tells us about the movements of our body.

Vestibular System:

the system in the inner ear that is concerned with controlling balance.