Glossary on the Topic Perception

Absolute threshold: The smallest amount of physical stimulus energy that is required to produce a sensation.

Ampulla: The enlarged area at the base of each semicircular canal that contains the receptors for the perception of body rotation.

Aqueous humour: The liquid that fills the space in the eye between the cornea and the lens.

Auditory canal: The passage that leads from the pinna to the eardrum.

Basilar membrane: The structure in the cochlea that moves when fluid is displaced in the cochlea and contains the receptors for sound waves.

Basket-shaped nerve endings: The receptors for pressure sensations that are located around the base of the hair cells.

Binocular depth cue: Information about depth that requires the use of both eyes (for example, retinal disparity).

Binocular (retinal) disparity: A binocular depth cue that is produced by the disparity between the images reaching each eye.

Blind spot: The area where the optic nerve leaves the eye; it contains no visual receptors.

Clairvoyance: The ability to perceive objects or events that cannot be perceived by the conventional senses.

Cochlea: The coiled, bony structure in the inner ear that contains the primary receptors for hearing.

Cone: One type of visual receptor that is located primarily in the central retina and is most important for colour vision and the perception of fine detail.

Cornea: The clear, tough outer covering of the eye. Dark adaptation: The process by which the eye becomes much more sensitive to light with increasing time under conditions of dim illumination.

Difference threshold (just noticeable difference): The smallest difference in physical energy between two stimuli that will enable someone to judge them as different.

Distal stimulus: A stimulus that actually occurs in the environment. Extrasensory perception: The field beyond usual sensory awareness that includes telepathy, clairvoyance, precognition, and psychokinesis.

Free nerve endings: The structures found in the skin that may be important in producing sensations of pain.

Fovea: The area in the central retina, containing many cones, where vision is most acute.

Illusion: A disparity between perception and physical reality.
Interposition: A monocular depth cue; when one object obscures part of another, it is judged to be nearer than the second object.

Iris: The coloured band of muscle tissue that surrounds the eye’s pupil. Kinesthesis: The sense of body movement that is provided by feedback from receptors located in the muscles, tendons, and joints.

Lens: The transparent, flexible eye tissue that focuses light on the retina.
Linear perspective: A monocular depth cue; parallel lines converge in the distance producing a perception of depth.

Meissner corpuscles: The receptors that are believed to produce pressure sensations in hairless area of the body.

Method of limits: The technique used in psychophysics to determine the absolute threshold.

Monocular depth cue: Information about depth that requires the use of only one eye (for example, interposition, shadows, texture gradient, and liner perspective).

Muller-Lyer illusion: The view that, of two lines of equal length, the one bounded by closed arrowheads is shorter than the one bounded by open arrowheads.

Olfactory cleft: The structure in the uppermost nasal cavity where the olfactory receptors are located.

Olfactory receptors: The structures in the nasal passages that are sensitive to smell.

Opponent-process theory: The theory proposed by Hearing that colour vision is produced by three different mechanisms that are sensitive to red-green, yellow-blue, and black-white, respectively.

Organ of Corti: The structure on the basilar membrane containing hair cells that are stimulated by the movement of the basilar membrane.

Ossicles: Three small bones that magnify the movements of the eardrum and direct them to the oval window.

Oval window: An opening in the cochlea.

Papillae: Raised areas on the tongue that contain groups of taste buds.

Perceptual constancies: Our perception of various objects as unchanging in spite of the fact that our sensory awareness of them does change.

Photon: A particle of matter that makes up light. Physical primaries: The colours red, blue, and green which, when

Fixed as lights, can produce any colour in the visible spectrum. Pinna: The external part of the ear. Precognition: The ability to forecast the future. Proximal stimulus: The pattern of energy (or information) that actually reaches a sensory receptor.

Psychokinesis: The ability to influence the physical world by means of thoughts or wishes.

Psychological primaries: The colours red, green, blue, and yellow, which subjects feel (by introspection) cannot be analysed into other colours.

Psychophysics: Study of the relationship between the physical characteristics of a stimulus and the psychological sensations it produces.

Pupil: The dark center of the eye through which light enters. Resonance (or place) theory: The theory that sensations of pitch are

Due to the responsiveness of different areas of the basilar membrane to sounds of different frequency.

Retina: The area at the back of the eye containing the structures that are sensitive to light—the rods and cones.

Rod: One type of visual receptor that is located primarily in the peripheral retina and that is important for seeing in dim light.

Saccule: One of the two parts of the vestibule in the inner ear. Semicircular canals: Three structures in the inner ear that is sensitive to the rotation of the body.

Sensation: A subarea within the field of perception that focuses mostly on the detection of energy and the working of the sense organs.

Signal detection theory: The view that any judgment in a psychophysical study is due to the actual sensitivity of the observer and the psychological factors that affect decision-making.

Size constancy: The judgment of the size of a given object as constant even though the size of the image it produces on the retina can change dramatically at different distances.

Shape constancy: Our perception of the shape of an object as constant even though the shape of the image it produces on the retina can change markedly.

Taste buds: The organs that are sensitive to taste; they are located on  the top surface and sides of the tongue.

Telepathy: The ability to read another person’s mind. Telephone (or frequency) theory: The theory that differences in sensations of pitch are due to the firing of more hair cells to sounds of greater frequency.

Texture gradient: A monocular depth cue; the elements on a textured surface appear to come closer together as depth increases.

Tympanic membrane (eardrum): A thin tissue at the end of the auditory canal that vibrates in response to sound waves.

Unconscious inference theory: The view that size constancy is due to internal computation the observer makes, according to which he adjusts his retinal image size depending upon the perceived distance of the object.

Utricle: One of the two parts of the vestibule in the inner ear.

Vestibule: A structure of the inner ear that provides information about body tilt and acceleration.

Visible spectrum: The range of light wavelengths the eye is sensitive to, varying from violet (400 millimicrons) to red (700 millimicrons).

Volley principle: The view that, above a frequency of 1000 cycles per second, the hair cells of the basilar membrane do not fire to all sound waves reaching the ear but only to some of them.
Wavelength: The distance between successive wave peaks. Weber fraction: The unvarying ratio between the magnitude of a given stimulus and the magnitude of a second one that can be perceived as discriminably different from it.

Young-Helmholtz theory: The theory that colour vision is due to the action of three receptors that are sensitive to red, green, and blue stimuli, respectively.