Unit 4. Sensation and College Board - Acorn Book Course Description 6-8% (7-9% in past)
Overview A. Thresholds B. Sensory Mechanisms C. Attention D. Perceptual Processes
A. Thresholds Threshold Absolute threshold Just-noticeable-difference (jnd) Weber s Law Fechner s Law (Psychophysical scaling) Subliminal perception
Signal Detection Theory Chart Response Yes Response No Signal Present Signal Absent
Signal Detection Theory Correctly identifies stimulus present Response Yes Response No Signal Present HIT Signal Absent
Signal Detection Theory Fails to identify stimulus present Signal Present Response Yes Hit Response No MISS Signal Absent
Signal Detection Theory Incorrectly identifies stimulus as present when absent Signal Present Response Yes Hit Response No Miss Signal Absent FALSE ALARM
Signal Detection Theory Correctly identifies stimulus as absent Signal Present Response Yes Hit Response No Miss Signal Absent False Alarm Correct Negative
B. Sensory Mechanisms Vision The Stimulus Light Amplitude, wavelength, purity, saturation Structure of the Eye Lens, retina, rods & cones, fovea Bipolar cells and ganglion cells Optic nerve and blind spot
Figure 6.7 The eye Myers: Psychology, Ninth Edition Copyright 2010 by Worth Publishers
Figure 6.8 The retina s reaction to light Myers: Psychology, Ninth Edition Copyright 2010 by Worth Publishers
Table 6.1 Myers: Psychology, Ninth Edition Copyright 2010 by Worth Publishers
Color - Color - Color Chromatic vs. achromatic (Colors vs. black & white) Hue, brightness, saturation (Color, light-dark, purity of color) Subtractive mixture vs. additive mixture (filters vs. paints) Good Web Site on Color Mixing http://home.att.net/~rtruscio/colorsys.htm
Additive New colors are made by the combination of different colored lights The three colors used are Red, Green, and Blue This is used for television screens, video, and computer monitors
Source: http://en.wikipedia.org/wiki/color_mixing A simulated example of additive color mixing
Subtractive New colors can be made when paints, inks, markers, and other coloring media are combined The three colors used are Magenta, Yellow, and Cyan This is used in color printers
Source: http://en.wikipedia.org/wiki/color_mixing A simulated example of subtractive color mixing
http://home.att.net/~rtruscio/colorsys.htm The above site provides an informative explanation and description of color mixing Color Vision Mixing Light Mixing Dyes Paints Ink The Basic Three - The physics and biology of color mixing Painting Photography Printing Other Considerations
Color Vision Trichromactic theory Young-Helmholtz (three color receptors different wavelengths) Color blindness (dichromats, etc.) Processing at receptor level Opponent-process theory Hering, Jameson, Hurvich (three pairs of colorsensitive neurons) Negative afterimage Processing at receptive field level (thalamus)
Color Vision: From Weiten. Themes and Variations. 4 th ed. Brooks/Cole. 1998
Colors of the Rainbow R O Y G B I V Color is determined by wave length Red is the longest wavelength of visible light. Violet is the shortest Water (mist) refracts light into different wavelengths
Hearing The Stimulus Soundwaves Amplitude (Loudness), Wavelength or frequency (Pitch), Wave purity or mixture (Timbre)) Structure of the Ear Outer ear Auditory canal Middle ear Eardrum, Hammer, Anvil, Stirrup Inner ear Cochlea, Basilar Membrane
The Ear From Coren, Ward, & Enns. Sensation and 6 th ed. John Wiley & Sons, Inc. 2004 Outer Ear Auditory Canal Eardrum Middle Ear Hammer, anvil, stirrup Inner Ear Cochlea
The Inner Ear From Coren, Ward, & Enns Sensation and 6 th ed. John Wiley & Sons, Inc. 2004
Figure 6.16 Hear here: How we transform sound waves into nerve impulses that our brain interprets Myers: Psychology, Ninth Edition Copyright 2010 by Worth Publishers
Taste and Smell Taste (Gustatory Sense) Stimulus Chemicals Four taste receptors Smell (Olfactory Sense) Stimulus Chemicals Olfactory bulbs, olfactory cilia Pheromones Taste and Smell Demonstrations Raw Apple, Raw Potato, Raw Onion Jelly Bellies
Skin Senses Pressure Hot Cold Pain Gate control theory in pain perception
Internal Senses Kinesthesis Internal body position Muscle position Vestibular sense Balance Semi-circular canals in ear
C. Sensory Adaptation Sensory adaptation is a change in sensitivity to a stimulus that results from exposure to the stimulus. Examples include adapting to darkness, adapting to bright conditions, adapting to hot or cold conditions, adapting to the presence of odors, and many more.
Sensory Adaptation Light and Dark Adaptation Entering / Exiting a movie theatre One eye covered demonstration The eye has two types of photorecptors Cones (for color) Rods (for night vision)
Dark Adaptation Move into a darkened theater and two changes occur to increase sensitivity to light: The pupils enlarge. This admits more light onto the retina of the eye. Light-sensitive chemicals in the photoreceptors increase their concentration. This makes each photoreceptor more sensitive to light.
Light Adaptation Leaving the theater, you encounter bright light Your pupils constrict immediately, reducing the light reaching the retina The light-sensitive chemicals in the photoreceptors quickly bleach out, reducing the photoreceptors sensitivity to light
Preserving Dark Adaptation It takes 20-30 minutes to become fully dark adapted This is destroyed by exposure to light in a few seconds Rods are blind to red light Cover light source with red lens Read map with cones Rods remain dark adapted
Sound Adaptation Adaptation to loud noise Very loud sound small muscle in the inner ear contracts dampens sound vibrations being conducted by the ossicles (bones) to the chochlea Adaptation does not work well for sudden loud sounds, such as gun shots
Odor / Smell The sense of smell is probably the quickest sense - as a whole - to adapt We can detect amazingly low concentrations of some chemicals in the air (e.g., perfumes) but although the perfume is still in the air about us, we quickly cease to detect it
Taste Certain tastes may cause rather surprising (and unexpected) anomalies in other taste stimuli Eating artichoke makes sour substances taste sweet briefly Jujuba temporarily abolishes sweet sensitivity Spicy foods will also stimulate pain receptors
Touch Heat Cold Skin temperature receptors respond more to rate of change in temperature than to steady temperature This explains why hot bath feels hot at first, then cooler This explains why pool/ocean feels freezing at first, then comfortable cool Demonstration One Hand in Cold Water, the other in Warm Water
Pain Adaptation Acute pain tells us to get away from the painful stimulus Chronic pain tells us not to move something while it heals
C. Attention Selective Attention Bottleneck Theories of Selective Attention We have a limited capacity to attend to stimuli There is no limit to how much stimulation can be present Selective Attention allows us to select what to attend to Sometimes we seem to do it Other times it seems to happen to us
Selective Attention and the Cocktail Party Phenomenon Cocktail Party Phenomenon the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations then if someone over the other side of the party room calls out our name suddenly, we also notice that sound and respond to it immediately
Selective Attention and the Stroop Test Stroop Test Why is this task so difficult to do reading is an automatic process color naming is a controlled process automatic process of reading interferes with our ability to selectively attend to ink color
Early selection Bottleneck or Filter Models of Selective Attention David Broadbent (1958) proposed that physical characteristics of messages are used to select one message for further processing and all others are lost Attenuation Treisman (1964) proposed that physical characteristics are used to select one message for full processing and other messages are given partial processing Late Selection Deutsch & Deutsch (1963) proposed that all messages get through, but that only one response can be mad
D. Perceptual Processes Feature analysis Bottom-up processing Top-down processing
Is it a circus act? Or a couple dancing? Ambiguous or Reversible figure Feature analysis Detecting specific elements Assembling them in a more complex form
Bottom-up Processing Recognize Stimulus A progression from Individual elements to the whole Also called data-driven processing Combine features Detect Specific Features
Bottom-Up Processing must be largely data-driven because it must accurately reflect events in the outside world The information is determined mainly be information from the senses (not from your expectations)
Top-Down Processing A progression from The whole to the elements Form perceptual hypothesis about the nature of the stimulus as a whole Also known as schemadriven processing Select and examine features to Check hypothesis Recognize Stimulus
Top-Down Processing In many situations your knowledge or expectations (or schemas) will influence your perception In this case a schema is a pattern formed earlier in your experiences.
Abstract concepts tend to be referred to as higher level Concrete details are referred to as lower level Top-down occurs when a higher level concept influences your interpretation of lower level data Set or expectancy demonstrate top-down processing Ambiguous figures often demonstrate topdown processing
Visual Contrast Brightness contrast (gray on white appears darker than gray on black) Mach Bands (Series of bands of increasing darkness - each strip affected by the neighboring strips) Lateral inhibition
Brightness Contrast
Principles of Perceptual Organization: Figure-Ground Grouping (Gestalt Principles) Proximity (Nearness) Similarity Continuity Closure
Closure
of Depth and Distance of Motion Perceptual Constancy (Size, Shape, Brightness) Perceptual Illusions Perceptual Set Perceptual Adaptation
Depth I could have sworn that mesa was a whole lot farther away
Necker cube (1)
Necker cube (2)
Necker cube (3)
Necker cube (4)
Necker cube (5)
Handouts DISTRIBUTION OF RODS AND CONES Bernstein (Colored pencils) Light-Dark Sensory Adaptation Demonstration (Eyepatch) Simple Compelling Demonstrations of Retinal Disparity ( Hole in hand etc.) DEMONSTRATING THAT SMELL IS AS IMPORTANT Beins (Jelly Bellies)
Monocular Depth Student Assignment Chart - Depth Cues (Study Guide / May be used in a variety of assignments) Color Vision Roygbiv (Demonstration) Pulfrich effect (Reading from Wikipedia)
Moon Illusion (Reading from Bad Astronomy by Philip Plait) The Big Picture - Gestalt applied The Neuroscience of Yorick's Ghost and Other Afterimages Mindsights Tables (Drawing by Shepard) Various Visual Illusions
The Janus Mask
The Magic of the Wundt-Jastrow Illusion
From: Gregory, R. I., Eye and Brain (2 nd ed.) New York: World University Library, 1973. (pp. 78-80.)