1. Ch. 4 AP Sensation pt. 1 What is sensation?
The process by which our sensory receptors and nervous system receive stimulus from the environment.
The absorption of energy, such as light or sound waves, by our sensory organs
Eyes
Ears
Tongue
Nose
Skin
Stimulus- a detectable input from the environment
Light- Vision
Sound- Hearing
Chemicals- taste and smell
Pressure, temp, and pain- touch
Orientation and balance- kinesthetic

2. Sensing the world: Basic Principles
Perception: the process of selecting and identifying information from the environment

3. Bottom-up processing: we start with the sensory receptors sand work up to higher levels of processing.
The human fovea can only focus on a very small area at one time
We fixate on one location for a moment and then move on to the next fixation. We take in little at each fixation and it’s through a pattern of saccades, a rapid movement of the eye between fixation points, that we take in our visual environment.

4. Top-Down Processing
Top-Down Processing The top-down process is driven by prior knowledge and expectations as well as our specific goals of the moment.
Suppose though, I asked you to find all the occurrences of the letter “P” in the image? Now as you scan the image the letter “P” should start to stand out a bit more and it’s possible that even the highly visible red letters start to fade into the background. At the very least you likely aren’t noticing the words they spell out.
You see more of what you’re looking for and less of what you aren’t.

5. Sensation Processing Bottom-up Top Down Recognize stimulus
Combine specific features into more complex forms
Detect specific features of a stimulus
Formulate perceptual hypothesis about the nature of the stimulus as a whole
Select and examine features to check hypothesis
Recognize Stimulus

7. Perception is how your brain processes the information.

8. Senses are nature’s gift that suit an organism’s needs.
Sensing the World
Senses are nature’s gift that suit an organism’s needs.
A frog feeds on flying insects; a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice.

9. Psychophysics
A study of the relationship between physical characteristics of stimuli and our psychological experience with them.
Physical World
Psychological World
Light
Brightness
Sound
Volume
Pressure
Weight
Sugar
Sweet

10. 22nd October 1850
A relative increase in mental intensity, [Fechner] realized, might be measured in terms of the relative increase in physical energy required to bring it about
(Wozniak, 1999).
Gustav Fechner
( )
Say what now??

11. Fechner’s Law
The magnitude of a sensory experience is proportional to the number of JNDs that the stimulus is above the stimulus
To put simply- he is describing Threshold- at what point will you notice a sensation?

12. Sensation- Thresholds
Absolute Threshold
minimum stimulation needed to detect a particular stimulus 50% of the time
Difference Threshold
minimum difference between two stimuli required for detection 50% of the time
Or also called the JND just noticeable difference (JND)

13. Absolute Thresholds for Humans
SENSE
STIMULUS
RECEPTORS
THRESHOLD
Vision
Electromagnetic Energy
Rods & Cones in the retina
A 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 room
Smell
Chemical substances in the air
Receptor cells in the nose
About 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 water
Touch
Pressure on the skin
Nerve endings in the skin
The wing of a fly falling on a cheek from a distance of about 0.4 inches

14. Weber’s Law
The idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount.
(Webers Fraction)

15. Subliminal Threshold
Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness.
Kurt Scholz/ Superstock

18. Backmasking http://jeffmilner.com/backmasking/index.html
Backmasking is the process of recording hidden messages in music which can only be revealed when a song is played backward. This technique was first used by the British Broadcasting Corporation in the 1920s, in an attempt to change people's negative attitude toward radio broadcasting

19. Selective Attention
The focusing of conscious awareness on a particular stimulus.

20. Signal Detection Theory (SDT)
Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on:
Person’s experience
Expectations
Motivation
Level of fatigue
Carol Lee/ Tony Stone Images

21. Transduction
is the process of changing one form of energy into another that your brain can use is called Transduction.
Remember Ethan in Sky High. He changes his body to slime. Solid form to liquid form. Change from one form of energy to another. Click the picture to watch power placement.

23. Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
OBJECTIVE 3| Describe sensory adaptation, and explain how we benefit from being unaware of changing stimuli.
Put a band aid on your arm and after awhile
you don’t sense it.

24. Activity- Sensation Movement Detectors

25. Sensory Restriction: Blakemore & Cooper, 1970
Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.