Sensation & Perception. What is Sensation? Passively receiving information through sensory inputs....
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Transcript of Sensation & Perception. What is Sensation? Passively receiving information through sensory inputs....
Sensation & Perception
What is Sensation?
• Passively receiving information through sensory inputs.
• Cells that detect physical energy are located in sense organs– Eyes– Ears– Nose– Tongue– Skin– Internal body tissue
What is Perception?
• The interpretation of sensory signals.
Example?
• Hearing your ringtone = sensation
• Recognizing the song = perception
• Hearing a voice = sensation
• Recognizing your mother’s voice = perception
How Many Senses Do We Have?
• More than five, though scientists disagree on how many.– Vision (eyes)– Hearing (ears)– Taste (tongue)– Touch (skin)– Smell (nose)
How Many Senses Do We Have?
• BUT WAIT! THERE’S MORE!– Skin can also sense heat, cold, pain, itching,
tingling– Ear also contains receptors for balance– Skeletal muscles contain receptors for a sense of
bodily movement.
Why are Senses Important?
• Help us survive• Even pain is a crucial part of our evolutionary
heritage– Alerts us to illness and injury
• But they also…– Entertain us– Amuse us– Soothe us– Inspire us
Sensation
• Sensation begins with sense receptors– Cells located in sense
organs• Receptors detect
appropriate stimulus—light, pressure, or chemical molecules—and convert the energy into electrical impulses that travel along nerves to brain.
Think of it like this…
• Sense receptors are like military scouts who scan terrain for activity.– Scouts can’t make decisions on their own.– Must transmit what they see to field officers (neurons).– Field officers report to generals at the command center
(brain).• Brain cells responsible for analyzing reports
(stimulus), combining information brought in by different scouts (senses), and deciding what it all means.
Think of it like this…
• “Field officers”—sense receptors—all use the same form of communication, a neural impulse, or pulse of electrical energy.
Sensory Receptors Neurons Brain
Doctrine of Specific Nerve Energies
• Different
What if we could sense everything?
• Life would be a headache.
• We can only take in a window of what is out there.– Known as the study of
psychophysics– Studies how the strength
or intensity of a stimulus affects the strength of sensation
Measuring the Senses
Absolute Threshold
• The smallest amount of energy that a person can detect reliably (50% of the time)
• Not really absolute: people detect borderline signals on some occasions and not others.
http://www.youtube.com/watch?v=wVhiezByMSUhttp://www.youtube.com/watch?v=4G60hM1W_mk
Absolute Threshold
No
Intensity
AbsoluteThreshold
Detected
YesYesNo No
Observer’s Response
Tell when you (the observer) detect the light.
Absolute Thresholds for HumansSENSE STIMULUS RECEPTORS THRESHOLDVision Electromagnetic
EnergyRods & Cones in the
retinaA candle flame viewed from a
distance of about 30 miles on a dark night
Hearing Sound Waves Hair cells of the inner ear
The ticking of a watch from about 20 feet
away in a quiet roomSmell Chemical substances
in the airReceptor cells in the
noseAbout one drop of perfume diffused
throughout a small house
Taste Chemical substances in saliva
Taste buds on the tongue
About 1 teaspoon of sugar dissolved in 2
gallons of waterTouch Pressure on the skin Nerve endings in the
skinThe wing of a fly falling on a cheek from a distance of about 0.4 inches
Difference Thresholds
• The smallest difference in stimulation that a person can detect reliably (50% of the time)
• The just noticeable difference
• Ex: Comparison of the weight of two blocks, brightness of two lights, or saltiness of two liquids.
http://www.youtube.com/watch?v=hyEoVN97J1c
Weber’s Law
• Idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount.
Weber’s Law• When comparing A and B, the difference threshold will depend on
the intensity or size of A.• The larger or more intense A is, the greater the change must be
before you can detect a difference.
Signal-Detection Theory
• Predicts how and when we detect the presence of a faint stimulus (signal).
• SDT assumes there is no single absolute threshold
• Detection depends on…– Person’s experience– Expectations– Motivation– Level of fatigue
Signal-Detection Theory
• Measurements for any given individual may be affected by the person’s general tendency, when uncertain, to respond, “Yes, I noticed a signal (or difference)” or “No, I didn’t notice anything.”
• Some people are habitual yea-sayers, others nay-sayers
Sensory Adaptation
• Diminished sensitivity as a consequence of constant stimulation.
• Ex: Put a band aid on and after a while, you don’t sense it.
Sensory Adaptation
• Hold your hand over one eye and stare at the dot in the middle of the circle.
• Gradual change from light to dark does not provide enough contrast for visual receptors firing at a steady rate.
Sensory Deprivation
• Some become disoriented, confused, restless, or grouchy.
• Some enjoy limited periods of deprivation, and some perceptual and intellectual abilities actually improve.
http://www.youtube.com/watch?v=dtZNjzeShYw
Selective Attention
• Focusing conscious awareness on a particular stimulus to the exclusion of others.
• The ability to focus on one stimulus at a time.
• Allows a person to function in a world filled with many stimuli.
• People with ADD have trouble doing this.
Read this.
Now read it again.
Selective Attention
• Example: Cocktail Party Effect– Ability to listen to one voice among many.– To pay attention despite many distraction.
Inattentional Blindness
• The inability to see an object or a person in our midst.
• Is Google Glass dangerous?
https://www.youtube.com/watch?v=Yu3zlWVCcjY