1. Sensation and Perception UNIT 4 S ensation and perception form our world. Sensation is processed by physical receptors; perception is a psychological function of interpretation.

2. Sensory Processes Sensation Perception Sensation is the process of receiving information from the environment through remarkable receptors in the human body. Perception is the psychological process of organizing sensory information to make it meaningful. These two processes are intermixed.

3. Sensory Processes The distinction between sensation and perception

4. The body receives information through the five main senses. The Five Human Senses Hearing VisionTaste Smell Touch

5. An absolute threshold is the minimal amount of sensory stimulation needed for a sensation to occur.

7. Vision: The Stimulus Light = electromagnetic radiation; travels as a wave – Amplitude: height of waves; perception of brightness – Wavelength: distance between peaks; perception of color * The visible spectrum is only a portion of the total range of wavelengths

8. The Visual Spectrum

9. Vision is the dominant sense. Iris Pupil Cornea Retina Blind Spot

10. The Cornea The cornea is the outer covering of the eye. Cornea

11. The Iris The iris is a muscle that opens and closes in order to control the amount of light entering the eye. Iris

12. The Functions of the Lens Accommodation: the curvature of the lens adjusts to alter visual focus Problems with this lead to: Nearsightedness: close objects seen clearly; distant objects blurry Farsightedness: distant objects seen clearly; close objects appear blurry

13. The Pupil The pupil is the opening in the eye. Pupil Responds to light, emotions like fear, likes & dislikes

14. The Retina The retina is the back of the eye that has receptors for light. Retina

15. The Blind Spot The blind spot is where the optic nerve exits and there are no receptors for light waves. Blind Spot

16. Close your left eye and stare at the dot and move either forward or backward until the cube disappears. Blind Spot Demonstration

18. Rods Rods are visual receptors that “see” only black and white and are most sensitive in low light. Cones Cones are visual receptors that receive color and are most sensitive in daylight.

19. How many? Where concentrated? Sensitive to light? Sensitive to color? Rods 120-125 million Very sensitive No Periphery of retina Cones 7-8 million Center of retina Low sensitivity Yes Rods and Cones

21. Basics of Color Vision Wavelength Color Intensity (amplitude) Brightness

22. Color Vision Wavelength determines color – Longer = red / shorter = violet Amplitude determines brightness Purity determines saturation

23. Color Blindness the inability to distinguish colors affects more males (8%) than females (.5%) most common: inability to distinguish red from green

24. Color Vision Afterimages: Visual sensations that linger after the stimulus is removed; color of the image is the complement of the color you originally stared at Cones fire to balance out what we see - - complementary colors