SENSATION AND PERCEPTION

1. SENSATION AND PERCEPTION

2. Sensation – the process of receiving information from the environment “Bottom-up processing” – think of the sense as the bottom, the beginning of an experience Perception – our interpretation of what the incoming sensory info. means (WHAT WE MAKE OF IT) “Top-down processing” – complex brain interpretation (top of the body) *The first area of psychology studied – called Psychophysics (by G. Fechner) Before sensation can take place, sensory stimulation must meet threshold Threshold – the amount of stimulation needed to trigger a neural impulse

3. Absolute threshold – the minimum amount of stimulation needed to trigger a neural impulse 50% OF THE TIME Each of the senses has an established, scientific absolute threshold **THRESHOLD VARIES, BY PERSON, BY SITUATION Signal detection – ability to detect a weak stimulus when extra effort is made Just Noticeable Difference refers to the amount of change in the stimulus required before a difference is noticed Weber’s Law is a mathematical formula for that concept change in K (value for stimulus) K

4. A controversial threshold experience: subliminal stimulation Started with an experiment by James Vicary in 1957 The famous “Eat popcorn”, “drink Coca-Cola” experiment Vicary admitted it was a hoax before he died!!

5. Read – sensory adaptation Transduction – process by which energy is converted into neural impulse – at the receptor level for each sense The 5 senses: 1. Vision – the dominant sense Light – travels in waves, strikes an object, some wavelengths absorbed, others reflected back – the reflected light is what we perceive & label Amplitude = height of wave (intensity of color) Properties of light: Wavelength = frequency(length) of wave (hue) Saturation – purity of wavelength

6. ROYGBIV

7. Structure of the eye: 1. Conjunctiva 2. Cornea 3. Sclera 4. Iris 5. Pupil 6. Aqueous humor 7. Lens 8. Ciliary muscles & ligaments 11. Retina 12. Fovea centralis 9. Vitreous humor 13. Blind Spot 14. Optic Nerve 10. Choroid

8. Receptors in the retina: rods and cones Cones: used for color vision used for daylight vision located in center of the retina approx. 7 million each eye provide sharp, detailed vision contain photochemicals called OPSINS Rods: used for night vision used for white and black heavily packed into the peripheral area of retinaapprox. 120 million each eye provide rough outlines of shapes

9. H 4 + layers of cells process neural impulse from rods/cones – bipolar, amacrine, horizontal and ganglion cells B 4 layers A G

10. Theories of color vision: 1. Tri-chromatic Theory – Hermann Von Helmholtz Retina has receptors with chemicals (opsins) which respond to ONLY 3 light waves Those 3 lightwaves (ONLY) give us millions of hues

11. Feature detectors – Hubel and Wiesel Parallel processing

12. Opponent Process Theory – EwaldHering trichromatic signals from the cones feed into neural cells (bipolar, ganglion, etc.) which fire in an opponent fashion – red/green blue/yellow or white/black *In an on-off way, not at the same time This explains the afterimage - When staring at ½ of color pair, it tires, and its opposite fires when you look away.

13. Humans are trichromatic – see all three color pairs 8% of males are colorblind - dichromatic Monochromatic – see in black, whit e and greys 2. Hearing (Audition) Sound travels in waves like light Pitch is measured in Hertz (frequency) - Normal human hearing range: 500 to 3,000 Hz (16-20,000 is possible)

14. Intensity (loudness) is measured in Decibels (amplitude) -Noises above 130 can be painful -85 db on a daily basis can do damage TINNITUS – ringing in the ears: a warning sign of hearing damage Hearing loss usually begins in the high ranges

15. STRUCTURE OF THE EAR: INCOMING SOUND WAVE • Outer ear: • Pinna • Auditory Canal Tympanic Membrane – vibrates at freq. of sound wave • Middle Ear: • Hammer (malleus) • Anvil (incus) • Stirrup(stapes) Oval window – ditto TM • Inner ear • Cochlea • Basilar membrane contains hair cells

16. Hair cells: 20,000 per ear are attached to basilar membrane, wave back & forth in fluid. That movement causes a an electrical impulse to fire in connected nerve cells Hair cells do not regenerate!!! Damage them and they’re gone forever!! • Types of hearing loss: • Conductive deafness • Nerve (sensorineural) hearing loss Theories of pitch:

17. 3. Cutaneous Sense (Touch) – also known as a somatosense Only 3 types of receptors give us all of the sensations we experience: **More sensitive areas of body have more receptors Pressure Temperature Pain Pain is least adaptive and necessary for survival! Babies and other animals deprived of touch are stunted physically, mentally and have high mortality rates Pain fibers are smaller than temp. and pressure fibers. – body has both “slow” pain and “fast” pain cells

18. **Gate Control Theory – The spinal cord acts as a gate which can block the small slow pain fibers & release endorphins when pressure and/or temp. fibers are stimulated

19. Olfaction (smell) Receptors are Olfactory bulbs – located high in nasal cavity in Olfatory Epithelium Odor molecules lock into receptors sites on bulbs like key into lock – only scents with receptors can be registered Smell is a chemical sense and a companion to taste *The most primitive sense – olfactory nerve is not routed through the thalamus *The olfactory nerve is routed alongside the hippocampus, so smell is very evocative

20. 5. Gustation(taste) Bumpy, porous surface of tongue - Papillae Under that layer lie the receptors – Taste Buds • Food must be in solution form to seep down to taste buds Receptors encircle the tongue, do not exist in the center of the tongue The types of receptors: Sweet, salty, sour, bitter and umami (savory) Taste buds do regenerate!! They regenerate more slowly with age

21. ALL OF THE SENSES WORK IN COMBINATION IN A PROCESS CALLED SENSORY INTERACTION 2 important companion senses: *Kinesthetic sense - position of body and limbs *Vestibular sense – system of semi-circular canals located in inner ear -gives us our sense of equilibrium. Fluid in canals moves with our movement These 2 + cutaneous sense give make up the somatosenses

22. PERCEPTION Perceptual organization – studied by Gestalt psych. since mid-1800s Grouping Principles: *Proximity, similarity, continuity, closure and connectedness all contribute to patterns we perceive http://graphicdesign.spokanefalls.edu/tutorials/process/gestaltprinciples/gestaltprinc.htm Other Gestalt Principles: reversible figure and figure-ground

23. DEPTH PERCEPTION - Recognizing distance and 3 dimensional depth in space around us A Nature or Nurture Issue!! Visual Cliff – test for depth perception in infants - Created by Eleanor Walk and Richard Gibson

24. Depth cues: 1. BINOCULAR CUES – require both eyes *Retinal disparity – the 2 ½ inch difference between the eyes creates 2 disparate images Brain overlaps/merges them - stereopsis *convergence – muscular cue: amount of tension created when eyes bring images together • More strain – object is closer 2. MONOCULAR CUES – only require 1 eye • Interposition (overlap) • Relative size • Linear perspective • Aerial perspective (relative clarity) • Texture gradient • Relative height • Relative motion • Light & shadow

25. Relative Height Linear perspective Relative size

26. Perceptual Constancies Size constancy, shape constancy, color and brightness constancies all keep our world unchanging Perceptual Set: -a predisposition to view the world from a particular perspective (a product of our schema) Context Effects: perception is influenced by the situation/environment (also a product of schema) **PSYCHOLOGY DOES NOT SUPPORT ESP AS SCIENTIFIC PHENOMENON!! READ Perceptual Adaptation ESP – 4 types: Telepathy Clairvoyance Precognition Psychokinesis (telekinesis)

27. Apparent motion: Autokinetic effect, phi phenomena and stroboscopic motion