Sensation and Perception

1. Sensation Approximate Absolute Thresholds Subliminal Perception Main Senses Perception Sensation and Perception

2. True or False? T/F People have five senses. T/F If we could see waves of light with slightly longer wavelengths, warm-blooded animals would glow in the dark. T/F People sometimes hear what they want to hear. T/F Some people can read other people’s minds. The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system: neural impulses.

4. Phi Phenomenon

5. Sensation and Perception Defined Sensation: • The detection of physical energy emitted or reflected by physical objects. • Sense Receptors: • Specialized cells that convert physical energy in the environment to chemical and electrical energy in the body. Perception: • The process by which the brain organizes and interprets sensory information. Transduction: • Transformation of stimulus information into nerve impulses (electrical).

6. Sensation Absolute Threshold: • Smallest quantity of physical energy that can be reliably detected by an observer. Difference Threshold: (Just Noticeable Difference) • Smallest difference between two stimuli that can be reliably detected by an observer. Weber’s Law: • Thresholds increase in proportion to the background. • When you are in a noisy environment you must shout to be heard while a whisper works in a quiet room.

7. Sensation Signal Detection Theory: • Divides a sensory signal into two processes: • Sensory process • Decision process • After receiving a weak stimulus you will: • Hit: Detect a signal that was there. • False Alarm: Says the signal was there when it was not. • Miss: Fail to detect a signal when it was present. • Correct Rejection: Correctly say the signal was absent when it was not there.

8. Approximate Absolute Thresholds • Vision: • Candle flame seen from 30 miles on a clear, dark night. • Hearing: • Tick of a watch from 20 feet in very quiet conditions. • Smell: • Drop of perfume diffused throughout a three-room apartment. • Taste: • .0356 ounce of table salt in 529 quarts of water. • Touch: • Bee wing falling on your cheek from a height of 1 centimeter.

9. Sensation • Sensory Adaptation: • Reduction or disappearance of sensory responsiveness that occurs when stimulation is unchanging or repetitious. • Brain responds more readily to new stimuli. • Sensory Deprivation: • Absence of normal levels of sensory stimulation. • Selective Attention protects us from sensory overload- • Not capable of fully processing all incoming sensory information. • We focus attention on selected aspects of the environment and block out others.

10. Subliminal Perception • Definition: Below threshold. • We can process some information from stimuli too weak to recognize. • Effect of Subliminal Stimulation: A subtle, fleeting effect on thinking. Does subliminal advertising work? • No. The goal of using subliminal advertising is to increase the likelihood that you will buy a particular product.

11. Main Senses Main Senses: (theoretical) • Visual • Audition • Tactile (touch) • Gustation (taste) • Olfactory • Proprioception(kinesthetic in parietal) • Immunological

12. Vision Why are we so dependent on our visual sense? Would we be as advanced as we are today without it? Fun Facts: • More information comes from our eyes than any other senses. • Our eyes see through visible light. • Our eyes pick up these light waves. • Color itself is not a property of the external world. • It is derived from the wavelength of visible light.

13. Colorblindness • Prevalence: One out of twelve men and one out of two hundred women. • Protanomaly (one out of 100 males): Red-weakness, Deuteranomaly (five out of 100 males): Green-weakness, Dichromasy • Monochromats:People who are totally colorblind. • Dichromats:People who are blind to either red-green or yellow-blue.

14. Colorblindness

15. Vision • Humans: • Lack certain pigments found in primate eyes. (our sclera is white) • Contrast in color between our facial skin, sclera and irises. • Gorillas: • Low contrast between their eyes and facial skin.

16. Afterimages : Sensations that linger after the stimulus is removed.Fix your eyes on the dot in the center of the flag.

17. Trichromatic Theory • There are three types of cones:red, green, and blue. • The colors we see are the result of a combination of the differing amount of light absorbed by the three types of cones. Rods: Dim light. (better with edges and curves) • Concentrated in the periphery. Cones: Color vision. (very poor at night) • Concentrated in the fovea. Ganglion cells: • Neurons in the retina of the eye. • Gather information from receptor cells.

18. Path from Eye to Visual Cortex light photo-receptors bipolar cells ganglion cells visual cortex LGN

19. Vision • Cornea • Transparent front part of the eye that covers the iris, pupil, and anterior chamber. • Refracts light and aids in focusing. • Optic Nerve • Transports sensory material to optic chiasm. • Iris • Provides color to the eye. • Fovea • Responsible for sharp central vision. • Necessary for reading, TV, driving. • Any activity where visual detail is important. • Pupil • Black circular/slit opening in the center of the iris. • Regulates the amount of light that enters the eye. • Retina • Back of eye. • Contains receptors.

20. Gestalt Principles of Perception Principles that describe the brain’s organization of sensory information into meaningful units and patterns. Proximity: • Things near each other are grouped together. Closure: • The brain will fill in gaps in order to make a whole. Similarity: • Things that are alike are perceived as belonging together. Continuity: • Lines and patterns are perceived as continuing in time and space.

21. Gestalt Principles of Perception Perceptual Set: • Readiness to detect a particular stimulus in a given context.

22. Gestalt Principles of Perception • Law of Pragnanz • Figure-Ground Organization • Isomorphism • Laws of Perceptual Grouping

23. The Herman Grid Gestalt Principles of Perception

24. Figure-Ground Distinction Figure: Entity perceived to stand apart from the background. Ground: Background against which a figure appears.

25. Perceptual Constancies • Size constancy • The perception of an object as the same size regardless of the distance from which it is viewed. • Shape constancy • Tendency to see an object as the same shape no matter what angle it is viewed from. • Brightness constancy • We perceive an object as having a constant lightness even while its illumination varies. • Color constancy • An inclination to perceive familiar objects as retaining their color despite changes in sensory information.

26. Perceptual Cues Superposition • Monocular distance cue in which one object, by partially blocking another, is perceived as being closer. Linear Perspective: • Two parallel lines appear to converge at the horizon. Elevation: • The higher on the horizontal plane an object is, the farther away it appears.

27. Depth Perception (seeing in 3D) Monocular cues: Depth cues requiring only one eye. Binocular cues: Depth cues requiring both eyes.

29. Hearing Fun Facts: • Sense of hearing never turns off at one time or another. • Cerebellum • Uses the fluid in the cochlea ( part of the semicircular canals) to aid in balance. • Organ of Corti (pronounced: cortee): • Structure in the cochlea containing hair cells that serve as the receptors for hearing. • Sensory receptors called hair cells turn air pressure changes into neural signals. Major Divisions: External, Middle, Inner

30. Decibel Level for Common Sounds

31. Auditory Pathway middle ear oval window eardrum organ of Corti cochlear

32. Hearing If a tree falls in a forest and no one is around to hear it, does it make a sound?

33. Tactile Fun Facts: • We have more pain nerve endings than any other type. • The least sensitive part of your body is the middle of your back. • The most sensitive areas of your body are your- • Hands, Lips, Face, Neck, Tongue, Fingertips, Feet • Shivering is a way your body has to get warm. • There are approximately 100 touch receptors in your fingertips.

34. Taste Fun facts: • Your sense of taste can replace itself. • Single taste bud contains 50-100 taste cells • Each taste cell can represent all 5 taste sensations. • Taste buds are the structures on the tongue that contain taste receptor cells. • An adult has about 10,000 taste buds. • Taste receptors die and are replaced every 7 days. • The number of taste buds decrease with age. Taste: • The ability to respond to dissolved molecules and ions called tastants. • Detect taste with taste receptors clustered in taste buds.

35. Taste Five primary taste sensations: • Salty-helps an animal suffering from Na+ deficiency. • Sour-detects acids in food. • Sweet-detects glucose in food. • Bitter-typically defective or rotten compounds. • Umami-glutamic acid salts such as MSG.

36. Anatomical Pathway taste buds thalamus medulla primary somatosensory cortex anterior-insular cortex

37. Olfaction Olfaction: • Sense of smell Olfactory bulbs: • Brain sites of olfactory processing Pheromones: • Chemical signals released by organisms to communicate with other members of the species. Detecting Odors: • Odorant binding protein (OBP) makes the detection of odors possible. • A nasal gland coats airborne molecules with OBP to facilitate detection by the receptors in the olfactory epithelium.

38. Variations in Odor Sensitivity • Women have a better sense of smell than men. • The ability to smell diminishes with age. • Smell acuity is greatest during early adulthood (ages 20-40).

39. Pheromones • Pheromones are chemicals produced by an animal that affects the behavior of another animal through scent. • Receptors in the vomeronasal organ detect pheromones.

40. Proprioception Defined: • The movement of arms and legs in relation to each other. Kinesthetic Sense: • Provides specific information about muscle movement, changes in posture, and strain on muscles and joints. • Receptors:stretch receptors and Golgi tendon organs (provide information about stretching and contraction of individual muscles). Vestibular Sense • The sense of equilibrium and awareness of body position in space. • 2 types of vestibular senses: — body rotation — gravitation and movement

41. Immunological Immune System: • Process in an organism that identifies and removes antigens by identifying items that are non-self.