PSYCHOLOGY. Chapter 5 SENSATION AND PERCEPTION PowerPoint Image Slideshow

Transcription

1 PSYCHOLOGY Chapter 5 SENSATION AND PERCEPTION PowerPoint Image Slideshow

2 Sensation and Perception: What s the difference Sensory systems with specialized receptors respond to (transduce) various forms of energy There s a just noticeable difference law. And we ve got Absolute Thresholds can detect stimulus 50% of the time. Advertisers try Subliminal Perception We can do processing from the bottom up, or from the top down. We start to ignore stimuli that are low level and don t change: Sensory Adaptation Inattentional Blindness: completely miss stuff

3 FIGURE 5.4 The amplitude or height of a wave is measured from the peak to the trough. The wavelength is measured from peak to peak... i.e. it s the height of the wave.

4 Vision the most relied on system Light Waves have 3 characteristics 1. Amplitude which determines brightness 2. Wavelength determines the color we see 3. Purity of wave determines saturation What do our eyes do to offer us up a vision of the world? Focus, focus & transduce. 1. The Cornea does the first focus and then 2. Light travels through the Pupil which is a round hole in the Iris (the colorful part of your eyes)

5 So far so good what s next? 3. Light hits the lens, and gets more focus 4. And then to it s final destination the fovea in the retina where transduction takes place. What does this transduction? Two types of photoreceptor cells get the ball rolling. 1) Rods: sensitive to dim light but not wavelength (B&W). Lots o them, and they are spread around fairly evenly. 2) Cones: Sensitive to bright light and color, & concentrated in the fovea. Great detail.

6 The anatomy of the eye is illustrated in this diagram.

7 And the other type of cells? Other neurons connect these to ganglion cells that form the optic nerve (blind spot) and these cross mid brain at the optic chiasm How does this system deliver color vision? Trichromatic Theory (cone level) Opponent Process Theory (ganglion cells) Each has merit, and fits different system parts What about depth perception? We use binocular cues like disparity, plus monocular cues like linear perspective

8 FIGURE 5.12 This illustration shows the optic chiasm at the front of the brain and the pathways to the occipital lobe at the back of the brain, where visual sensations are processed into meaningful perceptions.

9 FIGURE 5.15 We perceive depth in a two-dimensional figure like this one through the use of monocular cues like linear perspective, like the parallel lines converging as the road narrows in the distance. (credit: Marc Dalmulder)

10 How about hearing/audition? Sound travels in waves through the air (in space, nobody can hear you scream) Wavelength translates to pitch or frequency Amplitude translates into loudness levels Purity gives tones richness or timbre Humans can hear from 20hz to 20,000hz What are the parts to this system, and how do they work together? Starting with 1. The Pinna or outer ear, sound then heads 2. Through the auditory canal to the

11 3. Eardrum or tympanic membrane, then the 4. Three bones (hammer, anvil and stirrup) 5. Vibrate the Oval Window, who s fluid then 6. Vibrates cochlear fluid which activates 7. Hair Cells in the Basilar Membrane Theories to explain how we hear? Yup! 1. Place Theory by Helmholtz (high pitches) 2. Temporal Theory (best for lower pitches) We can locate sounds thanks to binaural cues: interaural level & timing differences. Hearing loss: may be congenital or conductive

12 FIGURE 5.16 The ear is divided into outer (pinna and tympanic membrane), middle (the three ossicles: malleus, incus, and stapes), and inner (cochlea and basilar membrane) divisions.

13 Let s move on to Chemical Senses Gustation: Taste buds line the walls of the bumps on the tongue Molecules of food (dissolved in saliva) fit into receptors for 5 distinctly different tastes 1. Sweet 2. Salty 3. Sour 4. Bitter 5. Umami or yummy (and maybe one for fat) These get replaced every 10 to 14 days. You may have anywhere from 500 to 10,000 buds.

14 Okay, how does Smell work? 10 million cilia in the nasal cavity (plus mucus) 1000 different types of olfactory receptors respond to odorant molecules in the air Here today, replaced in 5 to 8 weeks VERY direct connections for processing, data sent to the olfactory bulb, then off to the limbic system and the olfactory cortex How about the Somesthetic Senses? Skin for touch, temp, pressure & heat Meissner s corpuscles respond to pressure Ruffini corpuscles respond to stretch Free nerve endings for thermoception (temp)

15 FIGURE 5.20 Olfactory receptors are the hair-like parts that extend from the olfactory bulb into the mucous membrane of the nasal cavity.

16 FIGURE 5.21 There are many types of sensory receptors located in the skin, each attuned to specific touch-related stimuli.

17 Aren t we forgetting something? What about Pain? Nociceptors in skin, muscles, joints and even some organs Signals may travel via large nerve fibers or small nerve fibers (speed varies) Inflammatory pain associated with tissue damage Neuropathic pain associated with damage to neurons in peripheral or central nervous system Treatment options depend on type of pain

18 Additional systems: Vestibular, Kinesthetic and Proprioception Vestibular organs near inner ear: fluid filled & use hair cells. We have a utricle, saccule and 3 Semicircular canals. For balance & posture Kinesthetic systems focus on body movements through space Proprioceptive systems for body position Data from joints, muscles, tendons and skin all routed through the cerebellum Enough about Sensation...What about Perception?

19 FIGURE 5.22 The major sensory organs of the vestibular system are located next to the cochlea in the inner ear. These include the utricle, saccule, and the three semicircular canals (posterior, superior, and horizontal).

20 Perception is when our brain interprets all this data into a meaningful / organized experience of the world. How so? Gestalt Psychologists believe that perception involves more than just combining sensory stimuli. The brain does more than just sum up available sensory data, and it does so consistently in predictable ways. Here are some perceptual principles: Figure / Ground relationships Proximity Closure Similarity Continuity Depth Perception? Two Dimensional Cues Linear perspective Relative Size Three Dimensional Cues Convergence Binocular Disparity

21 FIGURE 5.23 The concept of figure-ground relationship explains why this image can be perceived either as a vase or as a pair of faces.

22 FIGURE 5.24 The Gestalt principle of proximity suggests that you see (a) one block of dots on the left side and (b) three columns on the right side.

23 FIGURE 5.25 When looking at this array of dots, we likely perceive alternating rows of colors. We are grouping these dots according to the principle of similarity.

24 FIGURE 5.26 Good continuation would suggest that we are more likely to perceive this as two overlapping lines, rather than four lines meeting in the center.

25 Any other principles that help my brain organize the data? Perceptual Sets or expectancies Top Down Processing Bottom up Processing Illusions confound my perception process! Muller-Lyer Illusion based on experience in rooms (with corners) Moon Illusion the Apparent Distance Hypothesis - depth cues on the horizon

26 FIGURE 5.3 In the Mu ller-lyer illusion, lines appear to be different lengths although they are identical. (a)arrows at the ends of lines may make the line on the right appear longer, although the lines are the same length. (b)when applied to a three-dimensional image, the line on the right again may appear longer although both black lines are the same length.

27 Closure suggests that we will perceive a complete circle and rectangle rather than a series of segments. This OpenStax ancillary resource is Rice University under a CC- BY 4.0 International license; it has been reproduced & modified, but must be attributed to OpenStax, Rice University. Any unspecified modifications were carried out by Neil Walker.