Learn to differentiate between sensation and perception
Discover how skin makes our sense of touch possible
learn about the biological processes of sensation and how these can be combined to create perceptions.
Sensation, Perception & Vision
Learn about sensation, perception, and vision
Learn to distinguish between sensation and perception, describe the concepts of absolute threshold and difference threshold, and discuss the roles attention, motivation, and sensory adaptation play in perception
Introduction to Psychology from Saylor Academy
extrasensory perception (ESP): Perception that occurs without benefit of the known senses.
parapsychology: The study of paranormal phenomena.
telepathy: Communication of thoughts from one mind to another that occurs without using the known senses.
clairvoyance: The ability to perceive objects and events without using the known senses.
precognition: The ability to foretell the future.
psychokinesis: The ability to move objects by mental effort alone.
Sensation and Perception by 
Sensation, Perception and Action by 
Sensation and Perception
Sensation
Sensation is the process by which we receive, transform, and process stimuli that impinge on our sensory organs into neural impulses, or signals, that the brain uses to create experiences of vision, hearing, taste, smell, touch, and so on.
Sensory receptors: Specialized cells that detect sensory stimuli and convert them into neural impulses.
Psychophysics is the study of the relationship between features of physical stimuli, such as the intensity of light and sound, and the sensations we experience in response to these stimuli.
The absolute threshold is the smallest amount of a stimulus that a person can reliably detect.
The nineteenth-century German scientist Ernst Weber studied the smallest differences between stimuli that people were able to perceive. The minimal difference between two stimuli that people can reliably detect is the difference threshold, or just-noticeable difference
Signal-detection theory: The belief that the ability to detect a signal varies with the characteristics of the perceiver, the background, and the stimulus itself
Subliminal stimulation: sensory stimulation below a person's absolute threshold for conscious perception
Perception
The process by which sensations are organized into an inner representation of the world
Perception depends on your five senses: vision, hearing, smell, taste, and touch. Touch is also associated with pressure, warmth, cold, and pain
Feature detectors: neurons in the sensory cortex that fire in response to specific features of sensory information such as lines or edges of an object. discovered by David Hubel and Torsten Wiesel
selective attention: The process by which we attend to meaningful stimuli and filter out irrelevant or extraneous stimuli.
perceptual set: The tendency for perceptions to be influenced by one’s expectations or preconceptions.
Perceptual constancy: the tendency to perceive the size, shape, color, and brightness of an object as remaining the same even when the image it casts on the retina changes
shape constancy: The tendency to perceive an object as having the same shape despite differences in the images it casts on the retina as the viewer’s perspective changes.
size constancy: The tendency to perceive an object as having the same size despite changes in the images it casts on the retina as the viewing distance changes.
color constancy: The tendency to perceive an object as having the same color despite changes in lighting conditions.
brightness constancy: The tendency to perceive objects as retaining their brightness even when they are viewed in dim light.
visual illusions: Misperceptions of visual stimuli.
Sensory adaptation
Sensory adaptation: the processes by which organisms become more sensitive to stimuli that are low in magnitude and less sensitive to stimuli that are constant or ongoing in magnitude
Sensitization: the type of sensory adaptation in which we become more sensitive to stimuli that are low in magnitude. also called positive adaptation.
Desensitization: the type of sensory adaptation in which we become less sensitive to constant stimuli. also known as negative adaptation.
Vision
Vision is the process by which light energy is converted into signals that the brain interprets to produce the experience of sight
Visible light: the part of the electromagnetic spectrum that stimulates the eye and produces visual sensation
Hue: the color of light, as determined by its wavelength
British Scientist Sir Issac Newton discovered that sunlight could be broken down into different colors by means of a triangular solid of glass called a prism.
Use the mnemonic device Roy G. Biv to remember the colors in order from longest to shortest wavelengths (red, orange, yellow, green, blue, indigo, violet)
Trichromatic theory: A theory of color vision that posits that the ability to see different colors depends on the relative activity of three types of color receptors in the eye (red, green, and blue-violet).
opponent-process theory: A theory of color vision that holds that the experience of color results from opposing processes involving two sets of color receptors, redgreen receptors and blue-yellow receptors, and that another set of opposing receptors, black-white, is responsible for detecting differences in brightness.
An afterimage is what you see if you gaze at a visual stimulus for a while and then look at a neutral surface, such as a sheet of white paper
The Eye
Cornea: transparent tissue forming the outer surface of the eyeball
Iris: a muscular membrane whose dilation regulates the amount of light that enters the eye
Pupil: the black-looking opening in the center of the iris, through which light enters the eye
Retina: the area of the inner surface of the eye that contains rods and cones
Optic Nerve: the nerve that transmits sensory information from the eye to the brain
fovea: The area near the center of the retina that contains only cones and that is the center of focus for clearest vision.
Lens: a transparent body behind the iris that focuses an image on the retina
Visual acuity: sharpness of vision
nearsighted: People who have to be close to an object to discriminate its details
farsighted: see distant objects unusually clearly but have difficult focusing on nearby objects
Color Blindness:
Visual perception
Visual perception: the process by which we organize or make sense of the sensory impression caused by light that strikes our eyes
Top down processing: the use of contextual information or knowledge of a pattern in order to organize parts of the pattern
Bottom up processing: the organization of the parts of a pattern to recognize, or form an image of, the pattern they compose
Hearing
Audition: The sense of hearing
Sound or auditory stimulation: the vibration of molecules in a medium such as air or water
Pitch: The highness or lowness of a sound that corresponds to the frequency of the sound wave. Frequency is measured in hertz (Hz).
loudness: corresponds to the height, or amplitude of sound waves. expressed in decibels (dB).
The Ear
The ear is structured to capture sound waves, reverberate with them, and convert them into messages or electrical signals the brain can interpret
eardrum: A sheet of connective tissue separating the outer ear from the middle ear that vibrates in response to auditory stimuli and transmits sound waves to the middle ear.
ossicles: Three tiny bones in the middle ear (the hammer, anvil, and stirrup) that vibrate in response to vibrations of the eardrum.
oval window: The membrane-covered opening that separates the middle ear from the inner ear.
cochlea The snail-shaped organ in the inner ear that contains sensory receptors for hearing. the bony tube that contains the basilar membrane and the organ of corti
basilar membrane: The membrane in the cochlea that is attached to the organ of Corti.
organ of Corti: A gelatinous structure in the cochlea containing the hair cells that serve as auditory receptors.
hair cells: The auditory receptors that transform vibrations caused by sound waves into neural impulses that are then transmitted to the brain via the auditory nerve.
auditory nerve: The nerve that carries neural impulses from the ear to the brain, which gives rise to the experience of hearing.
Perception of Hearing
Place Theory: The belief that pitch depends on the place along the basilar membrane that vibrates the most in response to a particular auditory stimulus. Developed by Hermann von Helmholtz
Frequency Theory: The belief that pitch depends on the frequency of vibration of the basilar membrane and the volley of neural impulses transmitted to the brain via the auditory nerve.
The Volley principle: The principle that relates the experience of pitch to the alternating firing of groups of neurons along the basilar membrane.
Deafness
conduction deafness: A form of deafness, usually involving damage to the middle ear, in which there is a loss of conduction of sound vibrations through the ear. Also known as conductive deafness
nerve deafness: Deafness associated with nerve damage, usually involving damage to the hair cells or to the auditory nerve itself. Also known as sensorineural deafness
Smell
Olfaction: The sense of smell.
olfactory nerve: The nerve that carries impulses from olfactory receptors in the nose to the brain.
olfactory bulb: The area in the front of the brain above the nostrils that receives sensory input from olfactory receptors in the nose.
Smell contributes to the flavor of food
Odors are also keyed into memory and emotions
pheromones: Chemical substances that are emitted by many species and that have various functions, including sexual attraction.
Taste
Gustation is the sensory detection of food on the tongue.
taste cells: Nerve cells that are sensitive to tastes.
taste buds: Pores or openings on the tongue containing taste cells.
Primary taste qualities: sweet, sour, salty, bitter, and meaty or savory.
Skin Senses
The senses of touch, pressure, warmth, cold, and pain that involve stimulation of sensory receptors in the skin.
Skin is the body’s largest sensory organ
Touch and Pressure:
somatosensory cortex: the part of the cerebral cortex that processes information from our skin receptors and makes us aware of how and where we have been touched.
Temperature:
receptors for temperature are neurons located just beneath the skin
Pain:
Pain receptors are located not just in the skin but also in other parts of the body, including muscles, joints, ligaments, and the pulp of the teeth—the source of tooth pain.
Pain results when neurons called nociceptors are stimulated.
Gate-control theory of pain: The belief that a neural gate in the spinal cord opens to allow pain messages to reach the brain and closes to shut them out
Phantom limb pain: perception of pain apparently "in" limbs that have been amputated, often because of activation of nerves in the stump of the missing limb.
acupuncture: An ancient Chinese practice of inserting and rotating thin needles in various parts of the body in order to release natural healing energy.
Skin receptors:
Meissner’s corpuscles: respond to pressure and lower frequency vibrations
Pacinian corpuscles: detect transient pressure and higher frequency vibrations.
Merkel’s disks: respond to light pressure
Ruffini corpuscles: detect stretch
kinesthesia: The sense that keeps us informed about movement of the parts of the body and their position in relation to each other.
vestibular sense: The sense that keeps us informed about balance and the position of our body in space.
semicircular canals: Three curved, tubelike canals in the inner ear that are involved in sensing changes in the direction and movement of the head.
vestibular sacs: Organs in the inner ear that connect the semicircular canals.
