Chapter 3 Sensation and Perception
Questions We Will Be Addressingin This Chapter What is the difference between sensation and perception? How does information from my eyes and ears get to my brain? Why do some people need eyeglasses? How would my voice sound on the moon? Why can’t I taste anything when I have a cold?
Questions We Will Be Addressing in This Chapter (cont’d) Which is the largest organ in my body? How do sensations become perceptions? What determines how I perceive my world? How do I recognize familiar people? Can you “run out” of attention?
Sensing and Perceiving the World What is the difference between sensation and perception?
Sensation vs. Perception Sense: A system that translates outside information into nervous system activity. “Sensations” Perception: The process of making sensations into meaningful experiences.
Sensory Systems How does information from my eyes and ears get to my brain?
Sensory Systems Accessory Structure – structures that modify stimulus, e.g., outer part of ear Transduction – process of converting incoming physical energy into neural activity Receptors – specialized cells that detect certain forms of energy Adaptation – decreasing responsiveness to stimulus over time
Coding Sensations The absolute threshold Why does an “absolute” threshold vary? Internal noise Response criterion
Signal-Detection Theory What determines a person’s report of a near-threshold stimulus? Sensitivity is influenced by: Internal noise Stimulus intensity Capacity of the sensory system Response criterion is one’s internal rule “Bias”
Judging Differences Between Stimuli Weber’s Law Just-Noticeable Difference (JND) “Difference Threshold”
Seeing Why do some people need eyeglasses?
Light Form of energy known as electromagnetic radiation Visible light – just a tiny slice of electromagnetic radiation (400-750 nanometers) Light intensity – physical dimension of light waves; how much energy the light contains that determines its brightness Light wavelengths –refers to length of light wave and produces sensation of color
Converting Light Into Images • Photoreceptors – specialized cells in the retina that convert light energy into neural activity • Rods • Cones
Seeing Color Hue – the essential color determined by dominant wavelength of a light Saturation – purity of a color Brightness – overall intensity of the wavelengths making up light
Trichromatic Theory of Color Vision Any color can be produced by mixing pure versions of blue, green, and red light Three types of cones Short-wavelength cones Medium-wavelength cones Long-wavelength cones Theory cannot explain afterimages
Opponent-Process Theory of Color Vision Color-sensitive visual elements in the eye are arranged in three kinds of pairs. Red or green, blue or yellow, black or white Members of each pair oppose, or inhibit, each other. When one member of the pair is no longer stimulated, the other is activated.
Hearing How would my voice sound on the moon?
Sound The repeated fluctuation – rising and falling – in the pressure of a substance, -e.g., air
Psychological Dimensions of Sound Loudness Determined by amplitude of sound wave Examples Pitch Determined by frequency of sound wave Timbre Determined by complex wave patterns added to the fundamental frequency of sound
VIDEO: Cochlea and Ringtones Discussion Questions
Deafness Conduction deafness Nerve deafness
Auditory Pathways to the Brain Auditory nerve conveys information to the thalamus which then relays it. Thalamus relays the information to the primary auditory cortex Cells in the auditory cortex have preferred frequencies. Auditory cortex also receives information from other senses.
Coding Sounds Place Theory Cannot explain encoding of very low frequencies. Frequency Matching Theory Also called Volley Theory
The Chemical Senses:Taste and Smell Why can’t I taste anything when I have a cold?
Why “Chemical” Senses? Senses arise from the interaction of chemicals and receptors. Smell detects airborne chemicals. Taste detects chemicals in solution coming into contact with receptors inside the mouth.
Smell, Taste, and Flavor Smell and taste act as two components of a single system, known as flavor. Scent and taste pathways converge in the cerebral cortex. Both tastes and odors prompt strong emotional responses. Variations in nutritional state affects: One’s experience of taste and flavor. One’s motivation to eat particular foods.
Our Sense of Smell Unique relationship between smell and memory. Species variability in sensitivity to odor and dependency on smell for survival. E.g., humans have about 9 million olfactory neurons while dogs have 225 million. Many species have an accessory olfactory system that detects pheromones.
Sensing Your Body Which is the largest organ in my body?
Somatic Senses Senses not located in a specific organ but rather spread throughout the body. Cutaneous senses – include skins senses of touch, temperature, and pain. Kinesthesia perception – tells brain where parts of the body are; closely related to balance
Sense of Touch Important for survival. Skin is the body’s largest organ Covers nearly two square yards of surface area. Weighs more than 20 pounds. Has hair virtually everywhere on it.
Encoding and Adapting to Touch Information Two aspects of an object contacting the skin are encoded. Intensity is coded by both individual firing rate as well as the number of neurons stimulated. The location of the nerves stimulated allows the brain to “know” where the touch occurred. Detection of changes in touch provide most important sensory information.