Psychology Sensation and Perception Taste, Smell, Position, Movement, Balance, Touch & Quick Review
To view other note of Psychology Click Here.
Taste and Smell
Taste and smell are chemical senses. As light waves stimulate vision and sound waves stimulate sound, chemicals stimulate taste and smell.
Taste
Taste, or gustation, happens when chemicals stimulate receptors in the tongue and throat, on the inside of the cheeks, and on the roof of the mouth. These receptors are inside taste buds, which in turn are inside little bumps on the skin called papillae. Taste receptors have a short life span and are replaced about every ten days.
For a long time, researchers believed in the existence of four tastes: salty, sweet, sour, and bitter. Recently, researchers have suggested the presence of a fifth taste called umami. The spice monosodium glutamate (MSG) has an umami taste, as do many protein-rich foods. Taste is also strongly influenced by smell.
Smell
Smell, or olfaction, happens when chemicals in the air enter the nose during the breathing process. Smell receptors lie in the top of the nasal passage. They send impulses along the olfactory nerve to the olfactory bulb at the base of the brain. Researchers theorize that there are a great many types of olfactory receptors. People perceive particular smells when different combinations of receptors are stimulated.
Remembrance of Smells Past
The sense of smell is closely connected with memory. Most people have had the experience of smelling something, maybe a certain perfume or spice, and suddenly experiencing a strong emotional memory. Researchers don’t know exactly why this happens, but they theorize that smell and memory trigger each other because they are processed in neighboring regions of the brain.
Position, Movement, and Balance
Kinesthesis is the sense of the position and movement of body parts. Through kinesthesis, people know where all the parts of their bodies are and how they are moving. Receptors for kinesthesis are located in the muscles, joints, and tendons.
The sense of balance or equilibrium provides information about where the body exists in space. The sense of balance tells people whether they are standing up, falling in an elevator, or riding a roller coaster. The sensory system involved in balance is called the vestibular system. The main structures in the vestibular system are three fluid-filled tubes called semicircular canals, which are located in the inner ear. As the head moves, the fluid in the semicircular canals moves too, stimulating receptors called hair cells, which then send impulses to the brain.
Touch
The sense of touch is really a collection of several senses, encompassing pressure, pain, cold, and warmth. The senses of itch and tickle are related to pressure, and burn injuries are related to pain. Touch receptors are stimulated by mechanical, chemical, and thermal energy.
Pressure seems to be the only kind of touch sense that has specific receptors.
The Gate-Control Theory of Pain
Researchers don’t completely understand the mechanics of pain, although they do know that processes in the injured part of the body and processes in the brain both play a role.
In the 1960s, Ronald Melzack and Patrick Wall proposed an important theory about pain called the gate-control theory of pain. Gate-control theory states that pain signals traveling from the body to the brain must go through a gate in the spinal cord. If the gate is closed, pain signals can’t reach the brain. The gate isn’t a physical structure like a fence gate, but rather a pattern of neural activity that either stops pain signals or allows them to pass. Signals from the brain can open or shut the gate. For example, focusing on pain tends to increase it, whereas ignoring the pain tends to decrease it. Other signals from the skin senses can also close the gate. This process explains why massage, ice, and heat relieve pain.
Quick Review
The Senses
- Psychophysics studies the relationship between the physical properties of stimuli and people’s experience of stimuli.
- Psychologists assess the acuity of our senses by measuring the absolute threshold and the difference threshold and by applying signal detection theory.
- Sensory adaptation is the decrease in sensitivity to an unchanging stimulus.
- Babies are born with all the basic sensory abilities and some perceptual skills, which develop and become more sensitive over time.
Vision
- The sense of vision depends on light, which is a kind of electromagnetic radiation emitted by the sun, stars, fire, and lightbulbs.
- We experience light as color, brightness, and saturation, which depend respectively on wavelength, amplitude, and complexity of light waves.
- The eye is composed of the cornea, the iris, the pupil, the lens, the retina, and the fovea. The lens adjusts its shape to focus light from objects that are near or far away in a process called accommodation.
- Dark and light adaptation are processes by which receptor cells sensitize and desensitize to light, respectively.
- The retina has millions of photoreceptor cells called rods and cones. Rods and cones connect via synapses to bipolar neurons, which connect to ganglion cells. The axons of the ganglion cells make up the optic nerve, which connects to the eye at the optic disk, also called the blind spot.
- After being processed in the brain, visual signals reach the primary visual cortex, where feature detectors respond to the signals.
- Color is a psychological experience created when the eyes and the brain interpret light.
- Trichromatic theory, or the Young-Helmholtz theory, states that there are three types of cones in the retina, which are sensitive to light of different wavelengths corresponding to red, green, or blue. This theory accounts for color blindness.
- The opponent process theory states that receptors act in opposite ways to wavelengths associated with three pairs of colors: red vs. green, blue vs. yellow, and black vs. white. The theory accounts for the perception of four primary colors. It also accounts for afterimages, or colors perceived after other complementary colors are removed.
- Gestalt psychology proposes that the perceived whole sometimes has properties that didn’t exist in the parts that make it up. An example is the phi phenomenon, in which an illusion of movement occurs when images are presented in a series, one after another.
- Gestalt psychologists describe principles people use to organize vision into units that make sense, including: figure and ground, proximity, closure, similarity, continuity, and simplicity.
- Binocular and monocular cues enable people to determine distance from an object.
- Perceptual constancy is the ability to recognize that an object is the same when it produces different images on the retina. Visual constancies relate to shape, size, brightness, color, and location.
- Visual illusions are misinterpretations of visual stimuli.
- Selective attention is the ability to focus on some pieces of sensory information and ignore others.
Hearing
- Hearing depends on sound waves. Sound has three features: loudness, pitch, and timbre, which depend respectively on wave amplitude, frequency, and complexity.
- The ear comprises the outer ear, the middle ear, and the inner ear. These parts contain the pinna, the eardrum, ossicles, oval window, cochlea, and cilia.
- Neurons in the ear form the auditory nerve, which sends impulses from the ear to the brain. The thalamus and auditory cortex receive auditory information.
- Place theory and frequency theory explain how people distinguish the pitch of different sounds.
Taste and Smell
- The stimuli for taste and smell are chemicals.
- Taste occurs when chemicals stimulate receptors in the tongue and throat.
- The five tastes are salty, sweet, sour, bitter, and umami.
- Smell occurs when chemicals in the air are inhaled into the nose. Smell receptors send impulses along the olfactory nerve to the brain.
Position, Movement, and Balance
- Kinesthesis is the sense of the position and movement of body parts.
- The sense of balance gives information about where the body exists in space and involves the vestibular system.
- The main structures of the vestibular system are the semicircular canals.
Touch
- The sense of touch encompasses pressure, pain, cold, and warmth.
- Pressure has specific receptors.
- The gate-control theory of pain proposes that pain signals traveling from the body to the brain pass through a gate in the spinal cord. This gate is a pattern of neural activity that prevents pain signals or admits them.
