1. Basic Principles of Sensation and Perception
Module 16

2. Sensation & Perception
Sensation – the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
(ex.) light energy entering eye, breeze hitting our body
Biological process
Perception – the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
(ex) recognizing a song, a baby’s cry
Psychological process (we create meaning)

3. Bottom-up Processing:
Analysis that begins with the sense receptors and works up to the brain’s integration of sensory information
Process built solely on physical stimuli
Ex. Detecting lines, angles, and colors that form a picture.

4. Top-down Processing:
Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experiences and expectations.
The processing of physical stimuli
Considering the title of a picture when viewing it:
“The Forest Has Eyes”

5. Selective Attention
Selective Attention - the focusing of conscious awareness on a particular stimulus
Cocktail party effect – the ability to attend selectively to only one voice among many
You are still capable of sensing things around you but you are only aware of what you are focusing
Ex. Cell phone and driving
SELECTIVE INATTENTION:
Inattentional Blindness – failing to see visible objects when our attention is directed elsewhere
(Who Dunnit?)
Change Blindness – failing to notice changes in the environment
Choice blindness – ways in which people are blind to their own choices

6. Transduction
Transduction - Conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret.
Psychophysics – the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them

7. Thresholds
Absolute Threshold - the minimum stimulation needed to detect a particular stimulus 50% of the time
Ex. Vision – candle burning 30 miles away from mountain top to mountain top in complete darkness
Ex. Sound – hearing a watch tick 25 feet away
But: detecting a weak signal depends not only on signal’s strength but also our psychological state.

8. Signal-Detection Theory
Signal detection theory - Predicts how and when we detect the presence of a faint stimulus (“signal”) amid background. Assumes that there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, physical state, and alertness.
Ex. Teacher speaking loud enough to break threshold for sound but student not motivated to pay attention
Ex. Being more sensitive to noises after watching a horror film )

9. Subliminal Processing
Subliminal – below one’s absolute threshold for conscious awareness
Can evoke a feeling but not influential in marketing products
Priming – the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response

12. Difference Threshold – the minimum difference that a person can detect between 2 stimuli
Ex. Detecting minute discrepancies in an instrument’s tuning
Ex. Noticing a change in weight of backpack
Also referred to as JND – Just Noticeable Difference
Weber’s Law - The principle that, to be perceived as different, two stimuli must differ by a constant percentage rather than a constant amount
Ex. Adding a quarter to an envelope will be a noticeable change in weight but not if you add a quarter to your wallet

13. Sensory Adaptation
Sensory Adaptation - Diminished sensitivity as a consequence of constant stimulation
After constant exposure to a stimulus, our nerve cells fire less frequently
Eyes- always moving (not noticeable) to avoid this
We perceive the world NOT exactly how it is, but as it is useful for us
Ex. Adjusting to cold pool water after a few minutes
Entering an odor filled room but not noticing after a while
Not feeling clothing on body

14. Automatic animation.
Instructor: you can tell students, “This will push your motion sensors into sensory adaptation.
For this to work, you must stare at the white dot in the center and never move your gaze.
When the motion stops, quickly stare at a nearby doorway, window, or a face next to you. Decide now what you will look at.”