5
Sensation Chapter and Perception
Sense Organs
*Sense
Organs: organs that receive stimuli
*Sensory Receptor Cells: specialized cells within the sense organs that send
neural impulses to the brain
Sensation Vs. Perception
*Sensation:
information coming into your brain organizing and interpreting the information
*Perception:
*Example: your ear receives a stimulus in the form of sound waves, you
perceive that your favorite song is on the radio
Sensory Limits (thresholds)
*Absolute
Threshold: the smallest magnitude of a stimulus that can be detected (the weakest detectable stimulus)
Vision: a candle flame seen at 30 miles on a clear, dark night Hearing: The tick of a watch under quiet conditions at 20 feet Taste: One teaspoon of sugar in 2 gallons of water Smell: One drop of perfume diffused into the entire volume of a 3-room apartment Touch: The wing of a bee falling on your cheek from a height of 1 cm *Difference
Threshold: the smallest detectable difference between two
stimuli
Sensory Limits Continued
*Webers Law: *The Difference Threshold between two things depends on the strength of the
original stimulus (the stronger the original stimulus, the bigger the changes must be in order for them to be noticed, yet changes in weak stimuli are very noticeable)
Eg. 100lbs, add 2 lbs
10 lbs, add 2 oz *Sensory
Adaptation: the perceived weakening of a sensation due to prolonged exposure to the stimulus
*Example: when you jump into cold water at first you feel freezing, but
after a few moments, the water does not feel as cold (sensory receptors are fatigued and do not detect the stimulus as strong as they first did)
Vision
*Must have light to see
Light is composed of waves that give us:
*Hue: of light gives us color *Brightness: of light *Saturation: of light (gives us pure versus paler colors)
Human Visual Spectrum:
ROY G. BIV
Parts of the Eye
*Cornea: *Iris:
coating on the surface of the eye
colored part of the eye that regulates the amount of light that enters
*Pupil: *Lens:
opening of the iris (the black part)
transparent portion of the eye that focuses light onto the retina fall here, sensor receptor cells are here
*Retina:
How the Eye Works
*The retina has two types of receptor cells: *Rods: cells that code information about light and dark, (located outside the
center of the retina 120 million cells each eye)
*Cones: cells that code information about light, dark, and color (located
at the center of the retina 6 million cells each eye)
*Fovea:
spot where the cones are concentrated (images focused directly onto the fovea are clearest because of the high concentration of cones)
*Optic
Nerve: nerve that carries visual neural messages to the brain (the area where the optic nerve attaches contains no rods or cones and therefore is a blind spot)
Color Blindness
*Most animals only see black, white and shades of gray
Total color blindness in humans is extremely rare (due to lack of cones or malfunctioning cones) Color-Blind people can usually see some colors and not others *Most common: Red-Green color blind: can see Yellow-Blue spectrum Rarer: Yellow-Blue color blind: can see Red-Green spectrum 8% of males are color blind Extremely rare in females(because of the XX pair)
Color Vision
*Trichromatic
Theory: The first level of color processing: are three different kinds of cones in the eye and that each respond to light in either red, blue, or green wavelengths therefore all sensations of colors result from stimulating a combination of these three cones.
*The Opponent-Process Theory: second level of color processing In addition to three types of cones (one for red, blue and green), there are opponent -process mechanisms which respond to either the red-green or the yellow-blue wavelengths Blue-Yellow, Green-Red, fires together, just one goes faster, and the other slower
Color Afterimages
*After
staring at one color for a long time we will see an afterimage of the opposite color
Visual Perception
*How is visual processed information into meaningful perceptions? *The Figure-Ground concept: when we see something, whatever
is in the background is the ground (we can change our perception of the same image by switching the figure and the ground)
Visual Perception Continued
*The
4 Gestalt(Deustch meaning whole) Principles of Perceptual Organization:
i.Proximity: things that are close together are grouped together in the
mind as if they belong together Closure: incomplete figures tend to be seen as complete because our brain fills in missing information Similarity: similar things are seen as being related Continuation: images are seen in ways that produce smooth continuation
*Visual
Constancy: the perception of objects remains unchanged, even when the sensation of the object is changing
*Brightness Constancy: we understand the brightness of an object does not
change even when the object is dimly lit Color Constancy: we understand that colors do not change despite different conditions of light Size Constancy: size does not change Shape Constancy: shape does not change
Depth Perception
*Monocular
Cues: cues in the environment that suggest depth and can be seen by only one eye.
*Binocular
Cues: uses both eyes
*Convergence: eyes angle inward as an object gets closer to us
Retinal Disparity: because each retina is a few inches apart, they have slightly different images and this helps with depth perception
Optical Illusions
are created using mostly monocular depth cues what we perceive is not always reality Examples: The Ames Room, Pronzo and Muller-Lyer illusions use monocular depth cues to trick the eye
*Illusions
Hearing
Sound energy, travels in waves Sound waves enter ear, transferred to temporal lobes for processing
Smell
Called _olfaction___ Airborne molecules enter the nose and are transferred to olfactory bulb in the brain for processing Difficult to classify smells Processed directly through the amygdala and hypothalamus and hippocampus
____________________________________________________ Smells can often trigger strong emotions/memories______
Taste
Called __gustation_______ Four basic tastes: Sweet Bitter Salty Sour
Taste buds: on the tongue, code for taste which is processed in the somatosensory cortex Flavor: influences by taste, smell and visual cues
Skin Senses
*Picks
up sensory information based on:
*Pressure
skin is very sensitive to pressure, but sensitivity varies depending on the are of the body
*Temperature
certain fibers detect warmth, certain detect cold, however, perception of temperature is not necessarily related to actual physical temperature
Pain Sensations
*Pain messages are sent through two distinct pathways: *rapid (first pain)
slow (second pain)
*Gate-Control
theory of pain: there are neural gates (endorphins) that control the transmission of pain impulses. The gate can be open (slow pain messages are not blocked, therefore we experience pain) or closed (slow pain messages are blocked, and we do not experience the pain)
Pain Sensations
Women have an additional pain-gate mechanism (that comes from the hormone estrogen) that men do not have (only activated in
childbirth) Men and women have different ways of processing and reporting pain Women process pain in emotional centers(check into limbic system to see how women and men process pain) Men process pain in logic centers Women report feeling pain sooner than men Men delay treatment for pain longer than women
Phantom Pain/Phantom Limbs
Phantom Limbs/Phantom Pain: amputees often feel the amputated limb as if it is still there and sometimes feel pain in the missing limb Theory: muscle memory the neurons in charge of missing limb dont know that it is gone but eyes see that the limb is gone mismatch between eyes and neurons As of July 2009, there are 904 soldiers who have lost limbs in the wars in Afghanistan and Iraq
Mirror-Image Therapy
Allows the eyes to see the missing limb as working, stops mismatch between neurons and eyes