1. Sensation and Perception

2. Sensation
• Process by which body gathers information about
environment
• Connects us to the world
• Sensation generally occurs in the sense organs
– vision (detects light waves)
– olifaction (sense of smell)
– gustation (sense of taste)

3. Perception
• Process by which the brain organizes and interprets
sensory information (“sensation PLUS perception”)
• Perception occurs in the brain
• 3 basic principles
o adaptive
o active
o no one-on-one correspondence between physical and
psychological reality

8. Perception
• Top-down processing
o “Conceptually-driven processing”
o Take information already existing in the mind to
interpret environment
• Bottom-up processing
o “Data-driven processing”
o Take stimuli from the environment and make attempts
to determine its meaning

9. Sensation
• Sensory receptors – Eyes, ears, nose, etc. detect physical energy
(light/sound/smell)
• Transduction – Translates physical energy into neural signals
• Absolute threshold – Each system’s minimal amount of energy
required to activate it
• Difference threshold – Each system’s minimal amount of energy
required to detect change from one level
of stimulus to another
– Just-noticeable difference (Weber’s Law)

10. Stroop Effect
• In this experiment, say the color of the word (not what
the word says)
• Example: For the word RED you should say “Red”. For
the word RED you should say “Yellow“
• As soon as the words appear on your screen, read the list
as fast as you can

13. Stroop Effect
• In this experiment, look at a picture of an animal and
say the name of the animal. Do NOT read the word
placed on the picture.
• For example: You should say "Cow" because the
animal in the picture is a cow.
• You should sat “Cat” because the animal in the picture
is a cat.

16. Vision
• Allows for the detection of movement, light, depth
perception
• Transduction – impulses from optic nerve carry visual
information from retina to optic chiasm;
neural messages then travel to thalamus
and into the visual cortex

17. Vision
• Motion perception
o Rods in retina sensitive to motion activate neurons in
the visual cortex
o 2 systems for processing movement
- Eye stationary as object moves
- Eye moves to maintain object at same place on the
retina

20. Vision
• Photoreceptors
o Cones
- Highest concentration in the fovea
- Require light to be activated
- Color vision/trichromatic theory (“photopic vision”)
- High visual acuity
o Rods
- Highest concentration in the retina
- Night vision (“scoptic vision”)
- Low visual acuity
- High sensitivity (esp. motion detection)

24. Vision
• Color blindness
• Inability to distinguish colors
• “Disease” is linked to the X chromosome, thus
males more likely than females to be color blind
• Most common condition is red-green color
blindness (difficulty distinguishing red and green)

28. Hearing
• Transduction
o Outer ear collects physical stimuli (sound waves)
o Inner ear carries movements via waves of fluid (in
ear drum) that generate neural signals
o Signals sent to thalamus then to temporal lobe

30. Hearing
• Volume – “loudness” determined by the height of sound
wave (amplitude)
• Pitch – refers to the frequency of the sound wave
(low B flat/high C tone)

31. Touch
• Protects body from injury, helps identify objects,
maintain body temperature
• 4 basic skin sensors (heat, cold, pain, pressure)
• Touch sensations differ throughout the body
• Transduction
o Sensory neurons in skin send impulses to spinal cord or
communicate with interneurons (that in turn stimulate
motor neurons)

33. Taste
• Refers to four basic tastes (sweet, sour, salty, bitter)
and protects us from injecting toxic substances
• Transduction
o Occurs in the taste buds
o Physical stimulus (soluble chemicals) activate taste
receptor neurons which carry information to thalamus and
primary cortex to help identify taste

34. Smell
• Detect danger (e.g., smoke, spoiled food) and/or
recognize familiar odors
• Transduction
o Physical stimulus (air molecules) enter nasal cavity
through nose
o Receptors in olfactory epithelium pass information
through the olfactory bulb to the primary cortex