CHAPTER 3 SENSATION Sensation and Perception Definitions Sensation
- Slides: 20
CHAPTER 3 SENSATION
Sensation and Perception Definitions Sensation – stimulation of the senses Perception – process of creating MEANING from sensations • The Nature of Sensory Processes The general character of sensation Some form of energy Stimulates receptor cell Sends out coded electrochemical signals Signals go to the brain Creation of sensory experiences Every sensory experience is an illusion created by the brain
– Sensory Thresholds n ABSOLUTE THRESHOLD – – – Minimum intensity of energy required for sensation Detected 50% of the time Differences between people Differences day to day for same person For each sense – low n JUST NOTICEABLE DIFFERENCE (JND) – Smallest change detectable (50% of the time) – Stronger the stimulation larger JND – Some senses are more sensitive n Bright light more than skin pressure
Vision Most important sense for humans The visual system Cellular path to the brain Light through CORNEA Through PUPIL – in center of IRIS Muscles in iris open/close pupil Through LENS – which focuses light Onto RETINA Inner lining back of eyeball Contains FOVEA Center of visual field Sharpest focus of images Receptor Cells In retina Sensitive to small part of spectrum of electromagnetic energy
THE HUMAN EYE
Receptor Cells (continued) Rods Light and dark only Just outside of fovea Chiefly responsible for night vision Cones Light, dark and COLORS Operate chiefly in daylight Mainly in center of fovea Less sensitive to light Need bright light Bipolar Neurons One axon – one dendrite Cones: ONE cone connects to ONE bipolar neuron Private line
THE VISUAL SYSTEM
AFTERIMAGES Ø Stare at the center of the upper square for about 20 seconds. Ø Shift your gaze to dot in the lower square Ø What happens? Why?
Afterimage Sense experience occurring after visual stimulus is removed New image becomes gray – not white • Never adapt completely All receptors would become insensitive Would see nothing Small eye movements move image on retina Connections from eye to brain Ganglion cells Axon form OPTIC NERVE to the brain
AFTERIMAGE Ø Look at GREEN bars, GREEN receptors become less sensitive; Ø Look away – Ø Only RED receptors able to respond, RED bars appear
Sensation and Perception Hearing Sound Caused by physical stimuli of sound waves Changes in pressure when molecules collide with one another then move apart Pitch High/low Determined by frequency of wave Measured by hertz – Hz
Hearing (continued) Loudness Intensity Determined by amplitude of wave Amplitude = height Measured by decibels Timbre “Texture” Pattern of overtones Waves that are different multiples of basic frequency (ex) Piano and violin playing same note sound different
SOUND MEASUREMENTS
THE HUMAN EAR
SMELL A. B. C. Very sensitive in humans 10, 000 times as sensitive as taste Pathway 1. Airborne molecules enter nose – activating odorant binding protein 2. Receptor Cells a. b. c. d. Nerve cells die – replaced every few weeks Only neurons to be replaced in the human body 1000 different receptors = 10, 000 different odors Requires little analysis by brain
SMELL (continued) 4. Receptor cells carry messages 5. Messages received by Olfactory Bulbs a. b. Information is recoded Information is received in the olfactory projection area in cerebral cortex Sensitivity 1. To odors even without being able to name them 2. Sex variable: females more sensitive 3. Age variable: older less sensitive
SMELL (continued) Sensitivity (continued) 4. Anosmia – loss of sense of smell a. b. c. Lose interest in food Reduce desire for sexual activity Can be dangerous 5. Cultural variable a. b. Korean-Americans more sensitive Question as to influence of culture and learning
TASTE A. Flavor = taste + smell B. Pathway 1. Chemical substances in food dissolve in saliva 2. Substances go between Papillae (small bumps) 3. Small bumps contain Taste Buds – 10, 000 a. b. Decrease with age On tip, sides, back of tongue
Taste (continued) 4. Chemical interaction causes neurons to fire 5. Messages to brain’s parietal lobe and limbic system C. Taste Qualities – Parts of Tongue 1. 2. 3. 4. 5. Sweet tip Salty tip Bitter back Sour sides No taste middle of tongue
Taste (continued) D. Sensory Adaptation 1. Get “accustomed” to strong flavors 2. Cross-adaptation a. b. c. Exposure to one Modifies taste sensation of other (ex) Brush teeth = sour orange juice
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