Sensation

1
Sensation

• Goals of the day
• Thresholds
• Vision
• Hearing
• Other senses

2
Basic definitions

• Sensation the detection of energy from physical
  environment and encoding it as neural signals in
  the brain
• Perception how we select, organize and
  interpret our sensations
• Psychophysics study of how physical energy
  relates to psychological experience
• Transduction process of converting physical
  energy stimuli into neural impulses

3
Basic elements

• Input from the Physical Environment
• Light waves
• Sound waves
• Molecules in the air that carry odors
• Other physical objects (can touch us)
• Receptors
• Rods and cones,
• Cochlea, basilar membrane with protruding hair
  cells
• Taste buds
• Olfactory bulbs,
• Nerve endings on skin

4

• Information processing
• Centers in Brain where information from sensors
  register

5
How much sugar do you need in your coffee before
it tastes sweet?

• We perceive things in with regard to intensity
  (quantity, how much) and quality
• Thresholds are related to intensity
• Absolute threshold minimum stimulation needed
  to detect a stimulus-- where you can detect it at
  least 50 of the time.

6
Evolution and threshold differences

• One of the first things we notice about sensation
  are differences in sensation thresholds
• sense of smell dog vs. human (bomb sniffing
  cancer sniffing)
• hearing (dogs)
• smell (men vs. women)
• taste - differences between people in perceiving
  spiciness in food (children v. adults--ability to
  detect pepper)
• vision antelope vs. human bear vs. human

7
If you put four teaspoons of sugar into your
coffee, how many more do you need to add to make
it taste sweeter?

• Difference threshold (just noticeable
  difference, J N D) the minimum difference a
  person needs to detect a difference between two
  stimuli at least 50 of the time
• The more intense the existing stimulus, the
  larger the change must be to be noticeable
• How much much the price of a CD go up before you
  notice the difference (2? ). How about the
  price of a new car?

8
Webers Law

• The difference threshold is a constant proportion
  of the stimulus
• Weight, 2 (10 lbs to 10.2 or 100 pounds 102
  pounds to notice the difference)
• Line length, 1
• Tones, 3

9
How bad do locker rooms smell?

• It depends on how long you are in one
• Sensory adaptation diminishing sensitivity to
  an unchanging stimulus

10
Why do things appear black and white when the
lights go down?

• Rods and cones
• receptor cells that convert light energy into
  neural signals (transduction)
• Rods cells that detect black, white and gray
  necessary for peripheral and twilight vision (120
  million)
• Cones cells that detect fine detail and color
  function well in well-lit conditions (6 million)

11
Frequency and amplitude

• Frequency wavelength
• Amplitude wave height
• Vision
• frequency color
• amplitude brightness
• Sound
• Frequency is to pitch as amplitude is to _____?
• frequency pitch
• amplitude loudness

12
Do bees see the same things as we do?

• Not completely.
• Bees detect ultraviolet wavelengths. We cant
  see them.
• Why?
• Different ecological niches of occupied by
  different species demand different perceptual
  sensitivities

13
How is our vision similar to your color TV?

• Young-Helmholtz trichromatic (3-color) theory of
  color vision
• any color can be created by combining light waves
  of 3 primary colors (red, green, blue)
• retina has 3 types of color receptors, each
  sensitive to red, green, blue light
• color vision works by additive principle (absorbs
  light)
• mixing these three colors produces over 1,000
  shades of color
• Color blindness
• lack of functioning red or green sensitive cones
  vision is dichromatic, making it difficult to
  distinguish red and green

14
What is more important to a soldier detecting
motion or camouflage? Why

• Feature debtors cortical neurons that respond
  to specific features of a scene
• edges, lines, angles, motion detectors, face
  detector, grandmother detector
• facial recognition uses 30 of the cortex, 10
  times what is used for hearing. why is facial
  recognition so important?
• motion detection. Registers first in the brain
• Parallel processing
• our brains do many things at once, by
  specialized, overlapping neural networks

15
The sensation of hearing

• Sound acoustic energy, rhythmic pulsation from
  vibrating object
• does tree falling is woods produce sound if no
  one is there to hear it?
• Frequency units Hz humans, 15 to 20,000 Hz
  dogs 15 to 50,000 Hz
• Amplitude units decibels

16
Theories of sound perception

• Place theory
• We hear different pitches because different sound
  waves trigger activity at different places along
  the cochlea's basilar membrane
• The brain recognizes a pitch depending on the
  place on the membrane from which it receives
  neural signals
• However, this only works with high frequencies
  low pitched sounds are not so localized
• As people age, they lose ability to hear high
  pitched sounds

17

• Frequency theory
• Basilar membrane vibrates with the incoming sound
  wave. This vibration triggers neural impulses to
  the brain at the same rates as the sound wave.
• The brain reads pitch from the frequency of
  neural impulses.
• This is how we perceive low pitched sounds

18
Other senses

• Proprioceptive (movement and body position)
• Kinesthesis system for sensing the position and
  movement of the muscles, tendons, and joints
• Vestibular sense position of the body in space
  by sensing gravity and movement

19

• Smell
• why do women have a more sensitive sense of smell
  than men?
• Taste
• why do we have preferences for particular types
  of tastes?
• Touch
• is pain a good thing?