Domain 2 Part 3Sensation/Perception
Sensation v. Perception
• Sensation: activation of our senses (eyes, ears, etc.)
• Perception: the process of understanding sensations
Absolute Threshold
• the weakest amount of a stimulus required to produce a sensation
Difference Threshold
• The smallest change in a physical stimulus that can be detected between two stimuli.
• Weber’s Law - The larger or stronger a stimulus, the larger the change required for a person to notice that anything has happened to it.
http://www.youtube.com/watch?v=wVhiezByMSU
Sensory Adaptation
• Decreased responsiveness to stimuli due to constant stimulation.
OUR SENSES
Our Most Dominant Sense
The most studied sense
Parts of the Eye
Parts of the Eye
How the Eye Works
1. Light enters eye through pupil and reaches the lens.
2. The lens focuses the light on the retina.
3. Photoreceptors known as rods and cones turn the light energy into neuron impulses.
4. Neuron impulses travel along the optic nerve to the occipital lobe in the brain.
http://www.youtube.com/watch?v=unWnZvXJH2o
Rods v. Cones
• Rods – Sensitive to low levels of
light – Basis of night vision – 75 to 150 million rods– See in black and white
• Cones – Require more light
before they begin to respond.
– Work best in daylight – 6 to 7 million cones – Sensitive to color
Color Deficiency
• Affects about 8% of American men and less than 1% American women
• It is a hereditary condition• Caused by cones not
functioning properly• Most people see some
colors• Very few people are totally
color-deficient
The Boy Who Sees Without Eyes
Hearing
Parts of the Ear
How the Ear Works1. Earflap (Pinna) directs sound waves down the auditory
canal. 2. Sound waves vibrate the eardrum. 3. Hammer, anvil, and stirrup vibrate and push against
cochlea.4. Pressure against the cochlea makes the liquid inside
move. 5. Tiny hairs inside the cochlea pick up the motion and
turn the sound vibrations into neuron impulses. 6. The auditory nerve carries the impulses to the cerebral
cortex. http://www.youtube.com/watch?v=fxZWtc0mYpQ
Deafness
• Conduction deafness– Bones of the middle ear
become rigid and cannot carry sounds inward
– Hearing aids can usually help
• Sensorineural deafness – Cochlea, hair cells, or
auditory nerve is damaged.
– Need a cochlear implant needed to correct deafness.
Smell
– When gaseous molecules come into contact with smell receptors in your nose allow you to smell.
– The message is then sent through the olfactory nerve to the brain.
Taste
Taste + Smell = Flavor • The sensation of flavor is actually a combination of taste and
smell.
http://www.youtube.com/watch?v=fxZWtc0mYpQ 3:33 to 4:29
Touch and Pain• http://www.youtube.com/
watch?v=mQoS62jEvNA• Receptors located in our skin
provide information about pressure, warmth, cold, and pain.
• Different nerve endings respond to pressure, temperature and pain
• Our brain interprets the amount of change and the place of the change
• Gate Control Theory of Pain – lessen some pains by shifting our attention away from the pain impulses
http://www.youtube.com/watch?v=ZfWO2wciIUY
Vestibular Sense
• Tells us where our body is oriented in space.• Our sense of balance.• Hair cells within the semicircular canals relay
information of our body orientation. When you turn your head, these canals also move. Inertia causes the fluid in the canals to resist changes in motion, which bends receptor hair cells projecting into the fluid.
• Over stimulation of the vestibular sense by movements such as spinning, falling, and tilting can cause dizziness and motion sickness.
Kinesthetic Sense
• Tells us where our body parts are.• Receptors located in our muscles and
joints send information to our brain about our limbs.
Perception
How we organize and interpret sensory information
I. Principles of Perceptual Organization
A. Proximity
When we see a number of similar objects, we tend to perceive them as groups or sets of those that are close to each other.
B. Continuity
We tend to see continuous patterns, not disrupted ones.
C. Similarity
When similar and dissimilar objects are mingled, we see the similar objects as groups.
D. Simplicity
We see the simplest shapes possible.
E. Closure
We fill in the gaps of missing information based on our previous experiences.
F. Figure-ground perception
• The ability to discriminate properly between a figure and its background.
• Also used for hearing. – Ex: When you are
following a person’s voice in a noisy room, that persons voice is the figure and the rest of the noise is the ground.
Perceptual Inference
• The phenomenon of filling in the gaps in what our senses tell us is known.
• Largely automatic and unconscious
Subliminal Perception
• Subliminal messages – brief auditory or visual messages presented below the absolute threshold so that there is less than a 50% chance that they will perceive it.
• 1974 subliminal advertising banned
• https://www.youtube.com/watch?v=OW9ou1kB1cU
Depth Perception
• The ability to recognize distances and three dimensionality
• Develops in infancy
http://www.youtube.com/watch?v=1VPaBcT1KdY&feature=player_embedded http://www.youtube.com/watch?
v=p6cqNhHrMJA
Monocular Depth Cues • Monocular Depth Cues
– Linear perspective (parallel lines appears to converge on a vanishing point)
– Relative height (more distant objects are higher)
– Relative size (more distant objects are smaller)
– Texture gradient- texture details, like roughness, diminish with distance
– Light and shadows –tell us about the shape and size. Brightly lit objects appear closer. While objects in shadows appear further away.
– Interposition – overlapping images lets us know which one is in front
Explain how the monocular depth cues are being used in this
painting.
Binocular Depth Cues
• Binocular depth cues – require two eyes– Retinal disparity – the greater the difference
between the images on your two retina, the closer the object
– Convergence – the greater your eye muscles must strain (or converge) to focus on an object, the closer the object (notice how hard your eyes strain when you focus on the tip of your nose).
Perceptual Constancythe ability to perceive an object is the same even as the illumination and
retinal image changes.
Shape Constancy- perception that shape of an object doesn’t change just because image on the retina does.
Perceptual Constancy
• Size constancy – perception that an object’s size remain the same even as the retinal image changes.
Perceptual Constancy
Color Constancy – the perception that familiar objects have a consistent color, even if changing illuminations alter the wavelength reflected.
Illusions
• Incorrect perceptions as a result of perceptual cues being distorted so that our brains cannot correctly interpret space, size, and depth cues.
http://www.youtube.com/watch?v=4GYwPPRDrHI