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Chapter 4

Chapter 4. Sensation and Perception. I. Sensory Processes. All incoming messages must be interpreted by the brain Sensation is not just physical, it is also psychological We create meaning from what we know Sensation – activation of our senses

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Chapter 4

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  1. Chapter 4 Sensation and Perception

  2. I. Sensory Processes • All incoming messages must be interpreted by the brain • Sensation is not just physical, it is also psychological • We create meaning from what we know • Sensation – activation of our senses • Perception – process of understanding sensation

  3. I. Sensory Processes • What affects how we sense and perceive stimuli: • How long we are exposed (ex: socks) • What we are focused on (voluntary v. involuntary cocktail-party phenomenon) • Sensation and perception happen through a process called: TRANSCUDTION • TRANSCUDTION: • signals transformed into neural impulses. • sent to thalamus first • Thalamus sends messages to correct part of the brain

  4. II. Sensation Vision • Light is reflected off objects and gathered by the eye • Wavelengths of light determine the hue we see • Longer wavelengths = infrared waves, microwaves, radio waves • Shorter wavelengths = ultraviolet waves, x-rays

  5. II. Sensation • Structure of the eye • Cornea: clear covering of the eye • Iris: colored, circular muscle – contracts/expands to control light • Pupil: opening in the eye (like shutter of a camera) • Lens: part of the eye that focuses an object on the back of the eye, focuses the light ***give me a finger*** image is projected upside down • Retina: like a screen, contains neuron receptors for light • Optic Nerve (Blind spot): part of the retina where the optic nerve exits – no receptors for light (p. 4)

  6. II. Sensation • Receptors in the Retina • Cones – first layer of cells, activated by light, color • Rods – respond to black and white • More Rods than cones • Peripheral **colored pencils** • Color Vision • Trichromatic theory • Red, green, blue • Opponent process theory • Red/green • Yellow/blue • Black/white • Fatigue of sensors p. 100 Pic taken with colorized scanning electron micrograph (SEM)

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  8. II. Sensation • Color defects, Color blindness • Red/green colorblindness most common (7-10% men) • Color blind test • Feature detectors • Width, depth, shape, curves, vertical lines, motion, and many others • Afterimage – firing of cones not used after viewing something in order to bring the visual system back in balance

  9. II. Sensation • Hearing – auditory sense, uses sound waves • Sound waves created by vibrations • Transduction to neural messages • Amplitude – determines loudness • Frequency – determines pitch • Characteristics of Sound • Pitch – how high or low a sound is • Timbre – complexity of sound (voices, instruments, sirens) • Intensity (decibels) – how loud more than 130 decibels = painful (p. 101)

  10. II. Sensation • Structure of the Ear • Ear canal – auditory canal (external structure) • Ear drum – skin stretched over entrance to ear, thin membrane; vibrates to sound, connected to 3 bones • Hammer • Anvil • Stirrup • Cochlea – snail shaped, fluid • Hair cells – receptor cells for hearing, when fluid moves, hair cells move, tuned to different frequencies, lost with age • Auditory Nerve – sense message to brain • Deafness – conduction v. nerve deafness

  11. II. Sensation C. Cutaneous Senses- touch • Cutaneous receptors respond to pressure, temp, pain • Receptors more sensitive in some parts of the body than others • All touch senses go to spinal cord • Purpose of pain: defense mechanism • Interpretation of pain: PLEASURE v. PAIN, depending on intensity, environment, circumstance (psychological)

  12. WHO???? • loves ice cream • enjoys eating broccoli • hates spicy, hot, or strongly flavored foods • has a hard time deciding what to order at a restaurant • always asks for sauces and dressings on the side • dives right into their food after being served • carefully tastes each food on their plate • adds a lot of salt • Has ever been called a picky eater

  13. Activity

  14. Let’s answer the following: • How did holding your nose and smelling mint affect the flavor of the food sample? • What are some reasons why it would be important to distinguish different tastes? • Genes are only one factor that determine your food preferences. What else might affect food preferences?

  15. II. Sensation • Smell (olfaction) • Chemicals • Strongly linked to memory (amygdala, emotion, and hippocampus, memory area, in brain) • Do not go to thalamus first, go directly to emotion/memory area in brain • Mechanisms of smell • Cilia – tiny hairs receive odor molecules, send to olfactory bulbs • Olfactory bulbs - generate code that brain interprets

  16. II. Sensation PHEROMONES • A study involving human subjects, conducted in Switzerland by Claus Wedekind, consisted of 44 males and 49 females. The men were given t-shirts and instructed to wear the T-shirts to bed for two consecutive nights to ensure that the T-shirts were totally saturated with pheromones. They were also given scentless soap and other toiletries and told to use them exclusively. At the end of the experiment, the t-shirts were put into a box and rated, on the basis of smell, by women. A number of boxes were filled with clean t-shirts to act as a control. • The women were then given the boxes and asked to rate them according to their reaction to the different scents, that is whether they found them pleasant or unpleasant. The results found that the women preferred the scents of the T-shirts worn by men with a dissimilar MSC gene. Many of the women commented that the scents reminded them of boyfriends or husbands.

  17. II. Sensation • Taste – chemical response • Tastebuds -Bumps on your tongue • Signals go down into tongue and connect to brain • Taste buds are all over tongue, insides of cheeks, and roof of the mouth • 4 types of tastes • Sweet – vital for energy, desire for sweet is built in • Salty – keeps body chemistry in balance • Sour – food gone wild (bad…old) • Bitter – detect poison

  18. II. Perception • The difference between sensation and perception = • Sensation is like getting data from environment • Perception is interpreting that date

  19. II. Perception • Top-down processing: I _ope yo_ _ad a g_eat w__ken_. use background knowledge to fill in the gaps • Schemas – mental representations of how we expect the world to be (from our experiences) • Perceptual Set – Predisposition to perceive something in a certain way. EXAMPLE: Finding objects in clouds

  20. II. Perception • Bottom-up processing • Aka feature analysis • Instead of using our experience to perceive an object – we use only the characteristics of the object to build a perceptoin

  21. II. Perception • Perceptual Constancies – our ability to maintain a constant perception of an object despite changes in angle, lighting, etc… • Size - close=larger image on retina, far away = small image

  22. II. Perception • Constancies • Size – keep things the same size • Color – knowing an object is the same color regardless of environment (lighting) • Brightness – keeps brightness of an object constant • Shape – objects viewed from different angles, but we know shape remains constant (coffee mug) • Space – ability to keep objects in the environment steady • Self-motion • Object-motion

  23. II. Perception B. Depth perception • Visual Cliff - experiment, proof of depth perception in early years • Binocular disparity – eyes see objects at different angles, when brought together, bring a sense of depth • With objects that are closer our eyes come together more, brain can sense muscle movement in eyes that bring them together, helps interpret that objects are closer • Visual Texture – depth perception based on how rough or smooth objects appear

  24. II. Perception • Perceptual Organization = Gestalt Rules • Gestalt Rules – helps give us the “big picture” Proximity - Similarity - Continuity - Closure -

  25. II. Perception • Illusions • Muller-Lyer • Reversible figure - • Subliminal perception – stimulation presented below the level of consciousness

  26. II. Perception • Psychology in your life • Do you have ESP? – Ganzfeld procedure • Telepathy –Reading someone’s mind • Clairvoyance – seeing or knowing something without being there, knowing when/what is happening at the moment something happens • Premonition or Precognition – Predicting the future • Pscychokinesis – influence over/moment of an object • Sixth sense • Full mull  mental hospitals

  27. Optical Illusions

  28. Most people think this is a trick, and that the shapes aren't actually the same in each image. Not so! • The illusion lies in the fact that the red and green triangles appear to be similar. They are not. The green one is 1 square taller than the red. To be similar, it would need to be 7·5 squares long - it's actually 8! This leads to a shallower gradient on its sloping side:

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