Sensation is the process of detecting stimuli through the senses, while perception involves interpreting and organizing those sensory inputs. Sensation is bottom-up processing, while perception involves top-down processing using memories and experiences. The document defines key concepts like absolute threshold, difference threshold, and signal detection theory, and describes how the different senses of vision, hearing, taste, smell and touch detect and process stimuli.

1. Sensation &
Perception
Basic Principles

2. sensation is the process of being aware of incoming stimuli.
• It processes information from the bottom up.
• Your vision, hearing, and other senses make you aware of the
raw sensory information.
perception the process of organizing and interpreting
incoming sensory information.
• Your memories, emotions, and experiences all affect how you
perceive, or interpret, the world around you through top-down
processing
• Top-down processing: Information processing that draws on
expectations and experiences to interpret incoming sensory
information.

3. List all the sensations that you would experience while sitting in a Roller
Coaster…

4. Read these sentences carefully and you will note
some odd things about them.

5. • A threshold is an edge, a boundary.
• Absolute Threshold
• Subliminal Message: messages played at a frequency
you cannot consciously perceive, into the sound of
ocean surf.
It is true that you can be influenced by a stimulus you are
unaware of. In one experiment, participants were shown a
brief image of an emotionally positive scene (like kittens) or
an emotionally troubling scene (like a dead body) so
quickly that the scene registered only as a flash of light.
Thresholds

6. • Absolute Threshold: The minimum amount of stimulation
needed to detect a particular stimulus.
If you stand in a quiet room away from a clock what the
minimum proximity you need to hear the tick tock.
• Difference Threshold: represents an edge, too—this time,
the minimum difference to detect that two stimuli are not
the same.
If I start increasing the volume on the dial..at what point
can you detect that its louder than before.
Thresholds

7. • Signal Detection Theory: predicts how and when we
detect the presence of a faint stimulus (signal) amid
background stimulation (noise).
• The dimmest start we can see in the night sky.
Signal detection formulas consider three kinds of variables:
• Stimulus variables—How bright is the blip on the radar
screen?
• Environmental variables—How much distracting noise is
there in the room with the radar equipment?
• Organismic variables—Is the operator properly trained
and motivated?
Signal Detection Theory

8. • Imagine that a radiologist is examining a CT scan,
looking for evidence of a tumor.
Tumor Present Tumor Absent
Doctor -YES HIT False Alarm
Doctor - NO MISS Correct Rejection
• In 2 instances the doctor correctly diagnosed, where as in
2 other instances there was a misdiagnoses.
• Law enforcement officers X-raying the contents of
luggage, or Air traffic monitors are other examples of
Signal detection.
Signal Detection Theory

9. • Sensory Adaptation means we filter out the non-changing
aspects of our environments.
When stimulation is constant and unchanging, you
eventually fail to respond because you usually don’t need
to.
Sensory Adaptation

10. Selective Attention

11. • The noise from TV while you are having a phone
conversation.
• Studying for an exam, and getting distracted or NOT.
• At this moment what are you paying attention to and what
are the things you are not paying attention to:
• Your clothes: how soft or coarse is there texture.
• Your shoes: the grip on your foot.
• Any previously written information on White board.
• The air temperature.
Selective Attention

12. The Nature of Light

13. The shorter wavelength = blue, purple- Higher wavelength = Red,
orange. Taller peaks = brighter colors. Shorter peaks = dull colors.
The Nature of Light

14. Vision

15. Pathway of Light-
• Cornea: the clear curved bulge in front of the eye. It is rich
with nerve endings.
• Iris: The ring of muscle tissue that forms the colored part
of the eye. Regulates pupil.
• Pupil: black circular opening in the middle of Iris.
• Lens: A transparent structure behind the pupil. Focuses the
light.
• Retina: Light sensitive surface at the back of the eye.
• Fovea: spot with concentration of cones.
• Optic Nerve: The bundle of axon going to the brain.
• Blind Spot: the exit point of nerves, absent of rods n cones
Parts of the EYE

16. RETINA
• It is made up of 3 layers of specialized cells. Deepest
layer of retina contains receptor cells.
• Receptor cells: change the light energy into nerve
impulses.
1. Rods: detect black, white, and shade of grey.
2. Cones: detect color and sharp details, and require
more light than rods.
• Bipolar cells: activated by rods and cones.
• Ganglion cells: neural cells with axons forming the
optic nerve.

17. Retina

18. The numbers of rods and cones in retina of human eyes.

19. Retina with Diabetic
Healthy Retina Retinopathy
Retinopathy in Human Retina

21. • Near sightedness: Light rays converging in front of the retina.
Is vision clear for near objects or far?
• Far sightedness: When light rays converge behind the retina.
Are the objects that are near blurred, or those that are far?
Near and Far sightedness

22. 1. The Trichromatic Theory of Color: All colors that we perceive are
a combination of three colors- Red, Green, and Blue.
2. Opponent-Process Theory: Color is processed by cones organized
in opponent pairs, red-green, yellow-blue, and black and white.
Light that stimulates one half of the pair inhibits the other half.
Two Theories of Color Vision

23. Photo-energy Transmission as Action
Potential

24. VISUAL PATHWAY

25. • Dr. Erskine & Ruhrberg, discovered that VEGF164, a
molecule usually known for triggering the growth of
blood vessels, is actually leading the nerve cells across
the chiasm and causing neural cells to cross over to
opposite sides of the brain during visual development.
They saw that in mice who lacked VEGF 164, there was
no crossing of ganglion cells at the optic chiasm. Who
knew that something we thought only would affect the
development of blood vessels in the brain would also be
responsible for neuron placement and organization!
Optic Chiasm

27. The Nature of Sound:
- Frequency- The pitch of the sound. A sound’s highness or
lowness, which depends on the frequency of the sound
wave.
- Intensity- Loudness.
How can you connect pitch and loudness to wavelength
and amplitude?
Hearing

29. • Sound wave travel through air, tissue, bone, and fluid
before they reach the receptor cells- the hair cells located
in Cochlea.
Structure of the Auditory System

30. Ossicles: a tiny mechanism consisting of three small bones
that transfer sound waves from the eardrum to the cochlea.
Hammer
Anvil
Stirrup
Cochlea is the Latin term for “snail.” It is a fluid-filled,
snail-shaped bony tube in the inner ear where sound waves
are changed to neural impulses.
oval window: The point on the surface of the cochlea that
receives sound vibrations from the ossicles.
Hair Cells: tiny projections in the cochlea that are the
receptor cells for hearing. When vibration causes the tips
of these hair cells to move even the width of an atom, the
vibrations cause the hair cells to generate neural impulses
that your brain can process

31. Hair Cells

32. • Two important cues to
locate sound sources:
• 1. determine which ear
hears the sound first
• 2. determine which ear
hears the louder, more
intense sound.
Sound Localization

33. AUDITORY PATHWAY
• Inner hair cells synapse on
bipolar cells forming the
auditory nerve
• Input from the left ear crosses
to the right inferior
colliculus
Medial geniculate nucleus
of the thalamus
Primary auditory cortex of
the temporal lobe

35. • TASTE: a chemical sense.
• Receptors are located on our
tongue that detect 5 tastes,
salty, sweet, sour, bitter and
scientist recently added
savory (meaty taste).
• We don’t all have the same
sensitivity for taste

36. SMELL: a chemical sense.
Receptors are called Olfactory cells.
Taste and smell interact to produce flavor.

37. • TOUCH: Our
skin is embedded
with different kinds
of receptors for
different
stimulations.