1. Sensation & Perception

2. How we perceive the world is much more than just an image transmitted to our brains!

3. Sensation- The process by which our sensory receptors & nervous system receive & represent stimulus energies from our environment.
Perception- The process of organizing & interpreting sensory information, enabling us to recognize meaningful objects and events.

4. How does our brain make sense of what we perceive?
Bottom-up processing- Analysis that begins with the sensory receptors & works up to the brain’s integration of sensory information
Top-down processing- Information processing guided by higher level mental processes, as when we construct perceptions drawing on our experience & expectations

5. Light & Color
Wavelength- the distance from the peak of one light or sound wave to the peak of the next.
Intensity- the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave’s amplitude

6. What is color?
A strawberry isn’t actually “red”. In fact, it doesn’t contain any quality of “redness”. The strawberry actually absorbs all light except red which is reflected back to our eyes. After that, our brain interprets this wavelength as “red”

7. How do we “see”?
Seeing is a process that involves the human eye, the thalamus, the occipital lobe and various other parts of the brain.

8. Outer Eye Structure

9. Outer eye structure
Pupil- The adjustable opening in the center of the eye through which light enters. Operates like the aperture of a camera.

10. Outer eye structure
Iris- a ring of muscle tissue that forms the colored portion of the eye around the pupil. Controls the size of the pupil opening

11. Outer eye structure
Lens- the transparent structure behind the pupil that changes shape to help focus images on the retina.

12. Inner Eye Structure

13. Inner Eye Structure
Retina- the light sensitive inner surface of the eye, containing rods & cones plus layers of neurons

14. Rods and Cones!!
Rods- retinal receptors that detect black, white, & gray. Primarily used for peripheral & twilight vision.

15. Rods and Cones!!
Cones- retinal receptors that are concentrated near the center of the retina & function in daylight or well-lit conditions.
Cones also detect fine detail and colors

16. Inner Eye Structure
Optic nerve- the nerve that carries neural impulses from the eye to the brain

17. Inner Eye Structure
Fovea- the central focal point in the retina, around which the eye’s cones cluster.

18. Inner Eye Structure
Blind Spot
Blind spot- the point at which the optic nerve leaves the eye. This creates a “blind spot” because no receptor cells are located there

19. Young-Helmholtz Trichomatic theory
The theory that the retina contains three different receptors.
One most sensitive to red
One most sensitive to blue
One most sensitive to green
When stimulated in combination, they can produce the perception of any color

20. Thresholds Hearing Test!
Absolute threshold- the minimum stimulation needed to detect a particular stimulus 50% of the time.
Hearing Test!

21. Signal Detection Theory
A theory predicting how and when we detect the presence of a faint stimulus or signal and background stimulation (noise). This theory assumes that there is no single absolute threshold & that detection depends on a person’s experience, expectations, motivation, and alertness.

22. Signal Detection Theory

23. What might affect our ability to detect signals properly?
Priming- the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response. Talking Dogs!

24. More on priming….
Backwards Lyrics

25. Perceptual Set
A mental predisposition to perceive one thing and not another. Let’s take a quick test……..

26. Write down what you see….

27. Write down what you see

28. Write down what you see

29. Write down what you see

30. Difference Threshold
The minimum difference between two stimuli required for detection 50% of the time. We experience the difference threshold as a “just noticeable difference” Thresholds

31. Subliminal messages…..
Subliminal- below one’s absolute threshold for conscious awareness at least 50% of the time.

32. Weber’s Law
The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage.

33. Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.