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SENSATION
Sensation -Experience of sensory stimulation, the activation or our senses
Perception -Process of creating meaningful patterns from raw sensory information
How does stimulation become sensation?
Transduction
Sensory Adaptation
Threshold
Table 4-1 gives the approximate absolute thresholds for the five major senses:
- SENSORY MODALITY - - - - - - - - - - - - - - - - - - - - - - - - - ABSOLUTE THRESHOLD
- Vision - - - - - - - - - - - - - - - - - - - - - - - - - Candle flame seen at 30 miles on a clear, dark night.
- Hearing - - - - - - - - - - - - - - - - - - - - - - - - - Tick of a watch under quiet conditions at 20 feet.
- Taste - - - - - - - - - - - - - - - - - - - - - - - - - 1 Teaspoon of sugar in 2 gallons of water.
- Smell - - - - - - - - - - - - - - - - - - - - - - - - - 1 Drop of perfume diffused into a three-room apartment.
- Touch - - - - - - - - - - - - - - - - - - - - - - - - - A bee's wing falling on your cheek from 1 centimeter above.
Threshold Notes
Absolute thresholds – minimum stimulation necessary to detect a stimulus 50% of the time (candle flame from 30 mi, watch ticking from 20 ft, wing of a bee falling on our check from height of ½ inch, single drop of perfume in three-room apartment, one teaspoon of sugar in two gallons of water
Signal detection theory—absolute thresholds vary depending on experience, motivation, expectation, alertness (sister hearing baby cry)
Subliminal – any signal below threshold (by definition you will detect it some % of time)
Difference threshold – the minimum difference that a person can detect between two stimuli
Weber’s law – to perceive a difference, two stimuli must differ by a constant minimum percentage (rather than a constant amount).
Demonstration – Place a stapler in one hand and a quarter in the other. Ask which weighs more. Then, balance both on psych books and ask which weighs more.
Relate to shopping – Cost of a soda goes up by 25 cents – very noticeable; cost of a television goes up by 25 cents, not noticeable
ENERGY SENSES
VISION
Vision is the dominant sense in human beings. Sighted people use vision to gather information about their environment more than any other sense. The process of vision involves several steps.
Step 1: Gathering light
Step 2: Within the eye
Cornea -The transparent protective coating over the front part of the eye
Pupil -small opening in the iris through which light enters the eye.
Iris -colored part of the eye.
Lens -transparent part of the eye inside the pupil that focuses light onto the retina
Retina -lining of the eye containing receptor cells that are sensitive to light
Step 3: Transduction
Transduction –process by which sensory signals are transformed into neural impulses
Receptor cell -Specialized cell that responds to a particular type of energy.
Rods -Receptor cells in the retina responsible for night vision and perception of brightness.
Cones -Receptor cells in the retina responsible for color vision
Fovea -Area of the retina that is the center of the visual field
Optic nerve - The bundle of axons of ganglion cells that carries neural messages from each eye to the brain.
Blind spot - Place on the retina where the axons of all the ganglion cells leave the eye and where there are no receptors Optic chiasm -Point near the base of the brain where some fibers in the optic nerve from each eye cross to the other side of the brain
Step 4: In the Brain
Color / Hue is a psychological sensation created in the brain obtained by the rods and cones from the wavelengths of the visible light spectrum
Electromagnetic Spectrum
Theories or color vision-
Trichromatic theory -Theory of color vision that holds that all color perception derives from three different color receptors in the retina
Opponent-process theory - Theory of color vision that holds that three sets of color receptors respond in an either/or fashion to determine the color you experience
Colorblindness -Partial or total inability to perceive hues.
Trichromats -People who have normal color vision
Monochromats -People who are totally color blind
Dichromats - People who are blind to either red-green (most common) or yellow-blue
SENSING SOUND: HOW DO WE HEAR SOUND WAVES
The vestibularocochlear nerve made up of the auditory and vestibular nerves carries nerve impulses for both hearing and balance from the ear to the brain
Parts of the ear-
Pinna Outer Ear
Ear canal – also called the auditory canal
Eardrum- Tympanic Membrane
Hammer, anvil, stirrup - (Ossicles) (aka -Malleus, Incus, and Stapes)The three small bones in the middle ear that relay vibrations of the eardrum to the inner ear
Oval window - Membrane across the opening between the middle ear and inner ear that conducts vibrations to the cochlea
Eustachian Tube -equalizes pressure in the inner ear.
Transduction takes place here:
- Cochlea - Part of the inner ear containing fluid that vibrates which in turn causes the basilar membrane to vibrate.
- Basilar membrane -Vibrating membrane in the cochlea of the inner ear; it contains sense receptors for sound
- Organ of Corti -Structure on the surface of the basilar membrane that contains the receptors cells for hearing
Auditory nerve -The bundle of neurons that carries signals from each ear to the brain
Pyschological Qualities of Sound
The ears contain structures for both the sense of hearing and the sense of balance.
Amplitude – the height of the wave , determines the loudness of the sound, measured in decibels
Frequency - The number of cycles per second in a wave; in sound, the primary determinant of pitch
Hertz (Hz) - Cycles per second; unit of measurement for the frequency of waves
Pitch - Auditory experience corresponding primarily to frequency of sound vibrations, resulting in a higher or lower tone
Decibel -The magnitude of a wave; in sound the primary determinant of loudness of sounds
Timbre is the complexity of the sound - distinguish your mom's voice from your sister
PITCH THEORIES- As with color vision, two different theories describe the two processes involved in hearing pitch: place theory and frequency theory.
Place theory -Theory that pitch is determined by the location of greatest vibration of the basilar membrane
Frequency theory -Theory that pitch is determined by the frequency on the basilar membrane
DEAFNESS
Hearing Loss
Hearing Loss
People can lose all or some of their ability to hear because of loud noises, infections, head injuries, brain damage and genetic diseases. Hearing loss is common in older people. There are several types of hearing loss:
- Conductive Hearing Loss: occurs when sound vibrations from the tympanic membrane to the inner ear are blocked. This may be caused by ear wax in the auditory canal, fluid buildup in the middle ear, ear infections or abnormal bone growth.
- Nerve Deafness -Sensorineural Hearing Loss: occurs when there is damage to the auditory nerve. This type of hearing loss may be caused by head injury, birth defects, high blood pressure or stroke.
- Presbycusis: occurs because of changes in the inner ear. This is a very common type of hearing loss that happens gradually in older age.
- Tinnitus: people with tinnitus hear a constant ringing or roaring sound. The cause of this ringing cannot always be found. Some cases of tinnitus are caused by ear wax, ear infections or a reaction to antibiotics, but there are many other possible causes of this disorder
TASTE (GUSTATION)
Transduction is on the Taste buds / Papillae-
Humans sense five different tastes: sweet, salty, sour, umami (savory) and bitter
Supertasters: Those with more taste buds for bitter food/ more sensitive - Evolutionary Advantage
Non tasters - less sensitivity
The actual organ of taste is called the "taste bud". Each taste bud (and there about about 10,000 taste buds in humans) is made up of many (between 50-150) receptor cells. Receptor cells live for only 1 to 2 weeks and then are replaced by new receptor cells. Each receptor in a taste bud responds best to one of the basic tastes. A receptor can respond to the other tastes, but it responds strongest to a particular taste.
Olfaction
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The sense of smell, called olfaction, involves the detection and perception of chemicals floating in the air. Chemical molecules enter the nose and dissolve in mucous within a membrane called the olfactory epithelium. In humans, the olfactory epithelium is located about 7 cm up and into the nose from the nostrils
Olfactory epithelium - Nasal membranes containing receptor cells sensitive to odors
Pheromone - Chemical that communicates information (sexual receptivity, danger, territorial markings) to other organisms through smell
VESTIBULAR SENSE – tells us about how our body is oriented in space.
Semicircular canals - Structure in the inner ear particularly sensitive to body rotation.
Vestibular sacs - Sacs in the inner ear that are responsible for sensing gravitation and forward, backward, and vertical movement
TOUCH
When our skin is indented, pierced, or experiences a change in temperature, our sense of touch is activated by this energy.
Gate control theory - Theory that a ‘neurological gate in the spinal cord controls the transmission of pain messages to the brain
PAG in the brainstem region can stop the transmission of the pain message
Pain is sensed in the Anterior Cingulate Cortex - frontal lobe
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