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Chapter 5

Textbook notes for chapter 5 of Psychological Science

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University of Toronto St. George
Ashley Waggoner Denton

Sensation and perception: - Sensation = the sense organs’responses to external stimuli and the transmission of these responses to the brain (188) - Perception = the processing, organization, and interpretation of sensory signals, resulting in an internal representation of the stimulus (188) - Sensation detects things and perception constructs information about our environments based on sensations (188) - Sensory coding = sensory organs’translations of stimuli’s physical properties into neural impulses (189) - There are different neural response patterns to different physical features (189) - Sensory coding begins with transduction, where sensory receptors produce neural impulses when they receive stimulation (189) - Most sensory information first goes to the thalamus, and information is then sent to the cortex where neural impulses are interpreted as sight, smell, sound, touch, or taste (189) - We can identify qualitative differences in stimuli, such as whether something is salty or sweet, because different sensory receptors respond to qualitatively different stimuli (190) - We can identify quantitative differences in stimuli based on the speed of a particular neuron’s firing (190) - Psychophysics examines our psychological experiences of physical stimuli (190) - Researchers present subtle changes in stimuli to subjects and observe how their sense organs respond (190) - Absolute threshold = minimum intensity of stimulation that must occur before you experience a sensation, ex. the faintest sound a person can detect 50% of the time (190) - Difference threshold = minimum amount of change for a person to detect the difference between two stimuli, ex. the difference between a salty taste and a non-salty taste (191) - Signal detection theory = the detection of a faint stimulus requires a judgement; it isn’t an all-or-nothing process, ex. an oncologist examining an x-ray for signs of cancer and finding some even though none exist based on outside knowledge of the patient and judgment that the patient is likely to have cancer (192) - Response bias = a subject’s tendency to report detecting a sensation even when none exists in an ambiguous trial (193) - Sensory adaptation = a decrease in sensitivity to a constant level of stimulation, ex. becoming accustomed to a certain smell in your house (193) - Weber’s law = the amount of physical energy needed to detect a change in sensation depends on the proportional change from the original stimulus (195) Taste: - Gustation = sense of taste (195) - The stimuli for taste are chemical substances from food that dissolve in saliva (195) - When food stimulates taste buds, they send signals to the brain, which produces the experience of taste (195) - Each taste experience is composed of the five basic qualities of sweet, sour, salty, bitter, and umami, which is savory (196) - Food preferences and pickiness comes partly from our different numbers of taste receptors, which affects our sensitivity to stimuli (196) - Through their eating behaviors before and just after birth, mother pass on their eating preferences to their children since children grow used to certain tastes in the womb (197) Smell: - Olfaction (smell) has the most direct route to the brain (198) - Smell occurs when receptors in the nose respond to odorants that pass through the nose and into the nasal cavity (198) - In the nasal cavity, the odorants come into contact with the olfactory epithelium, which is the thin layer of tissue embedded with smell receptors (198) - These receptors transmit information to the olfactory bulb, which is the brain centre for smell, located below the frontal lobes (198) - Smell information goes directly to other brain areas (198) - Odors stimulate several receptors and the activation pattern across several receptor types determines smell perception (199) - People have difficulty identifying what odors are, even if they know they are pleasant or unpleasant (199) - Loss of smell as people age is associated with mental deterioration (199) Touch: - Haptic sense = sense of touch that conveys sensations of temperature pressure, pain, and a sense of where our limbs are in space (200) - Haptic receptors for temperature and pressure are sensory neurons that end in the skin’s outer layer (200) - There are hot receptors and cold ones, although they can be triggered simultaneously by intense stimuli (200) - Most experiences of pain occur when damage to the skin activates haptic receptors (201) - The nerve fibres that convey pain information are thinner than those for temperature and pressure and are found in all body tissues that sense pain (201) - There are two different fibers for sharp immediate pain and dull chronic pain (201) - Myelinated axons respond more quickly than unmyelinated axons, so myelinated axons produce intense immediate pain and unmyelinated axons produce chronic dull pain (201) - Gate control theory of pain = for us to feel pain, pain receptors must be activated and a neural gate in the spinal cord must allow the signals through to the brain (202) - Pain is thus a perceptual experience (202) - Pain signals are transmitter by tiny nerve fibers, which can be prevented from reaching the brain by the firing of larger nerve fibers (202) - This can close a gate and prevent or reduce the perception of pain (202) - Pain is processed in the same areas of the brain as stress, fear, and anxiety, so the more anxious or fearful we are, the more open the gate will be to allow pain through (203) - Women are more sensitive to pain than men and have more complex pain management styles (203) - Pain management medication slows down the firing of neurons so patients become unresponsive to stimulation (204) Hearing: - Hearing results when the movements and vibrations of objects cause the displacement of air molecules (204) - Displaced air molecules produce a change in air pressure, and the pattern of that change is called a sound wave (204) - The wave’s amplitude determines its loudness (204) - Its frequency determines its pitch, measures in hertz (204) - Changes in air pressure produce sound waves that arrive at the outer eat and travel down the auditory canal to the eardrum, a membrane stretched tightly across the canal and marking the beginning of the middle ear (204) - The sound waves make the eardrum vibrate (204) - The vibrations are transferred to ossicles, which transfer the vibrations to the oval window, which is in the inner ear (204) - The oval windows vibrations create pressure waves in the inner ear’s fluid, so hair cells bend and cause neurons on the basilar membrane (which runs through the inner ear) to fire, producing sound (204) - Cochlear implants directly stimulate the auditory nerve (207) - After it is implanted, the person loses all hearing in that ear because sound no longer travels via the ear canal and inner ear (207) - Instead sound is picked up by a tiny microphone behind the ear and transmitted to the implant’s electrodes inside the inner ear (207) - We can figure out where sounds are coming from because sound waves reach one ear before the other (208) Vision: - Light passes first through the cornea, which is the clear outer covering of the eye (208) - The cornea focusses incoming light through refraction (208) - Light rays then enter and are bent farther
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