Sensation and Perception Sensation & Perception The interplay between the external world, physiological systems, and psychological experience How the external world makes impressions on our nervous system & how the nervous system organizes those impressions 1
Working Together Sensations: Detect environment and encode it into neural signals Perception: Select, organize, and interpret the sensations that result from these signals BiDirectional Influence Bottom up processing Information from the senses is sent for processing Top down processing Information from higher levels is sent down and influences perception of the world 2
Sensing the World Happens through our senses Vision, hearing, taste, smell, proprioceptive (touch/ movement) System specific stimuli Each system has a form of energy that it can detect and process Physical energy must exceed absolute thresholds (in some cases must also exceed other thresholds) Has transduction mechanisms to change physical energy into neural information then sends to specific brain areas Can be influenced by attention Vision Eye detects electromagnetic radiation (light) Movement Color Humans are visual creatures Light travels quickly, travels in straight lines, interacts with surfaces in the environment (is reflected or absorbed) b 3
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Information to the brain Passed to the visual cortex Processed in a parallel and distributed manner Connections between areas give us a sense of coherence Perceptual Processes Identifying everything and documenting it in detail is a lot of work, so your visual system takes shortcuts Our expectancies can guide what we see Gestalt principles of vision the sum is greater than the parts Help us quickly identify the nature of the stimuli 5
Depth Perception The environment provides cues for perception The lines tell us there is depth here So objects appear to change size These linear cues are often functional Size Constancy We see objects as maintaining their size If frog 1 were to move and become frog 3, we would assume that it were further away, not changing size Even though the size of image on retina has changed 6
Hearing Ear detects sound waves Wavelength determines frequency (pitch) of a sound Wave amplitude determines the loudness 0 decibels is the weakest sound detectable by humans Hearing can be damaged by sounds that are too loud and/or listened to for too long The auditory system 7
Passage to the brain Information is transmitted via the auditory nerve More complex than visual transmission Most sent to opposite side of the brain, but some to the same side 1. Place theory Each frequency vibrates a particular place on the membrane High frequency vibrations displace the membrane close to the oval window Low frequency vibrations displace the membrane closer to the tip of the cochlea We tend to lose the ability to hear high frequencies first 8
2. Frequency theory Each frequency determines how frequently the auditory nerve fires High frequency = more frequent firing Low frequency = less frequent firing 3. Volley Principle Clusters of nerve cells can fire in succession Even though each nerve cell is limited in how frequently it can fire, multiple cells could fire in turns Frequency theory is best for sounds below 1,000 times per second Combination of place and frequency is needed for sounds above 1,000 times per second 9
Skin Senses Skin is our largest sense system Responds to mechanical energy from pressure, temperature, or pain from intense stimuli Pain reduction Distraction Focused breathing Counterstimulation Chemical Senses Taste Bumps (papillae) on tongue contain receptors for taste (taste buds) Replaced about every 2 weeks Areas of the tongue more sensitive to salty, sweet, sour and bitter tastes Smell Top of the nasal cavity contains receptors for smell Linked to areas of the brain associated with feeling and memory 10
Kinesthetic & Vestibular Senses Kinesthetic: movement, posture, orientation Embedded in muscle fiber and joints Signal the state of muscles Vestibular: balance, movement Whether head is moving/tilted Receptors in semicircular canals of the ear 11