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This article explores the psychological aspects of sensation and perception, covering topics such as sensory information, absolute and difference thresholds, sensory adaptation, anatomy of vision and auditory system, depth perception, taste, smell, touch, pain, and the role of expectations and context. It also discusses how the brain processes visual and auditory information, theories of color and pitch perception, and the principles of perception.
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Psychological Foundations Sensation and Perception
Sensation • Sensory information • Includes vision, hearing, smell, taste, touch balance, body position, movement, pain, and temperature • Absolute threshold • Messages that are presented below the threshold for conscious awareness are called subliminal messages. • Difference threshold
Perception • How sensory information is interpreted and consciously experienced • Sensation is a physical process, whereas perception is psychological • Attention and motivation determine what is sensed versus what is perceived • Sensory adaptation
From Eye to Brain Note the optic nerve, optic chiasm and the pathways to the occipital lobe, where visual sensations are processed into perceptions
Visual Information in the Brain Visual information is processed in parallel pathways which can generally be described as the “what pathway” (the ventral pathway) and the “where/how” pathway (the dorsal pathway)
Light Waves and the Electromagnetic Spectrum Light enters the eye as a wave
The Visible Spectrum Different wavelengths of light are associated with our perception of different colors
Two Theories of How We See Color Trichromatic Opponent Process Color is coded in opponent pairs: black-white, yellow-blue, and green-red. Cells of the visual system are excited by one of the opponent colors and inhibited by the other. Explains why we can’t see greenish-red and why there are afterimages. Applies once the signal moves past the retina on its way to the brain • The cones respond to three wavelengths that represent red, blue, and green. • All colors can be produced by combining red, blue, and green. • Applies to visual processing on the retina
Depth Perception • Depth perception: ability to perceive spatial relationships in (3-D) space • Binocular cues • Monocular cues
Sound Waves • Sound waves travel into our ears at various speeds and amplitudes • Higher amplitudes are associated with louder sounds • High-frequency sound waves are perceived as high-pitched sounds
Two Theories of Pitch Perception Temporal Place Different portions of the basilar membrane are sensitive to sounds of different frequencies Place contributes to pitch perception for frequencies under 4000 Hz. Much higher frequency sounds can only be encoded using place cues. • Frequency is coded by the activity level of a sensory neuron. • Applies to frequencies of up to 4000 Hz
Sound Localization Monaural (one-eared) Each pinna interacts with incoming sound waves differently, depending on the sound’s source relative to our bodies. Binaural (two-eared) cues: • Interaural level difference • Interauraltiming difference
Types of Hearing Loss • Deafness • Congenital deafness • Conductive hearing loss • Sensorineural hearing loss
Taste Molecules from the food and beverages we consume dissolve in our saliva and interact with taste receptors on our tongue (below) and in our mouth and throat
Smell Olfactory receptors are proteins with pockets that identify molecules of chemicals in the air. This information is transmitted from the olfactory bulb to the brain
Touch Specific receptors in the skin convert stimulation to electrical nerve impulses, a process called transduction • Mechanoreceptors (below) respond to mechanical stimuli, such as stroking, stretching, or vibration of the skin • Thermoreceptors respond to cold or hot temperatures • Chemoreceptors respond to certain types of chemicals either applied externally or released within the skin
Pain Pain is adaptive because it makes us aware of an injury, and it motivates us to remove ourselves from the cause of that injury • Neuropathic pain • Inflammatory pain • Nociceptors are subtypes of chemoreceptors or mechanoreceptors that fire specifically to potentially tissue-damaging stimuli Expectations and context shape how we experience pain
Pain and the Somatosensory Cortex Pain is signaled via fast-conducting A-fibers, which project to the somatosensory cortex This part of the cortex is somatotopically organized—that is, the sensory signals are represented according to where in the body they stem from
The Vestibular System The major sensory organs of the vestibular system are located next to the cochlea in the inner ear
Gestalt Principles of Perception The brain creates a perception that is more than simply the sum of available sensory inputs
Figure-Ground Relationship The concept of figure-ground relationship explains why this image can be perceived either as a vase or as a pair of faces
Proximity The Gestalt principle of proximity suggests that you see (a) one block of dots on the left side and (b) three columns on the right side
Similarity When looking at this array of dots, we likely perceive alternating rows of colors We are grouping these dots according to the principle of similarity
Continuation Continuation would suggest that we are more likely to perceive this as two overlapping lines, rather than four lines meeting in the center
Closure Closure suggests that we will perceive a complete circle and rectangle rather than a series of segments
Multimodal Perception Multimodal perception is the effect stimulation of multiple senses has on perception. • Multimodal phenomena • McGurkEffect • Rubber Hand Illusion • Crossmodal phenomena • Double flash illusion • Ventriloquism effect
Why Do Psychologists Use Illusions? Perception scientists create illusions to explore perception, what parts of the brain are involved in interpretation of the illusion, and what variables increase or diminish the strength of the illusion.
Practice Question Based on what you have learned about pain, how might we treat pain other than pharmaceuticals?
Quick Review • What is the difference between sensation and perception? • How does vision work? • How do people see color and depth? • How does hearing work? • What are the basic anatomy and functions of taste, smell, touch, pain, and the vestibular sense? • What is perception? • What are some examples of gestalt principles and multimodal perception?
