1. Sensation and Perception: Vision Mr. Callens Psychology

4. 1. Sensation vs. Perception Sensation – The process through which the senses pick up information from our surroundings and transmit it to the brain to interpret. Perception – The process by which that sensory information is actively organized and interpreted by the brain. Three Definitions:

5. 2. Transduction Process where the receptors change or convert the sensory stimulation into electrical signals the brain can process.

6. 3. Adaptation The process of becoming less sensitive to an unchanging sensory stimulus over time Allows you to shift your attention to what is most important at any given moment

7. Process of Sensation Absolute threshold – The minimum amount of sensory stimulation that can be detected 50% of the time Difference threshold – The smallest increase or decrease in a stimulus required for sensation to be noticed 50% of the time – “Just noticeable difference” (JND)

8. Process of Sensation Ernst Weber (1795-1878) – Observed that the JND for all the senses depends on a proportion or percentage of change rather than a fixed amount of change

9. Vision People can only perceive a small part of the total electromagnetic spectrum.

10. Vision

11. 1. Reverse Image The eye perceives all images upside down in the back of the retina because of the way the light is reflected. The brain later turns these images right side up for you.

12. 2. Cornea Thin rounded covering over the eye that focuses broad light waves into a narrower beam.

13. 3. Pupil A round opening at the front of the eye that allows light waves to pass to the eye’s interior.

14. 4. Iris The circular muscle that surrounds the pupil and controls the amount of light entering the eye. Iris also contains the pigment that gives your eye its color. HD Eyeball

15. 5. Lens An oval structure that focuses the beam from the cornea and pupil even more narrow. Works almost in tandem with the iris.

16. 6. Retina A thin film at the back of the eye that contains cells that are sensitive to light. These cells begin the process of transduction by absorbing light waves.

17. Vision

18. What happens in Lasik Eye Surgery?

19. Vision Rods – Allow humans to see in black, white, and shades of gray in dim light – Take 20 – 30 minutes to fully adapt to darkness Cones – Enable humans to see color and fine detail in adequate light, but that do not function in dim light – Adapt fully to darkness in 2 – 3 minutes

20. Vision Trichromatic theory – First proposed by Thomas Young in 1802 – The theory of color vision suggesting that there are three types of cones, which are maximally sensitive to red, green, or blue, and that varying levels of activity in these receptors can produce all of the colors

21. Vision Opponent-process theory – The theory that the eye and the thalamus only respond to the combination of red/green and yellow/blue. – Cells will respond to one color versus the other in each pair based on stimuli. – Based upon the studies of afterimages.

22. Afterimages

26. Color Blindness Unable to distinguish two or more shades of colors Monochromats: total color blindness (world looks like black and white movies). Dichromats: red/green color blind (results in them seeing much more in blue and yellow)

27. Dichromats

28. Optical Illusions

29. A perceptual experience that preys upon the mind’s need to interpret depth, shape, and size, and create an image that in reality cannot or does not actually exist:

30. Optical Illusions Percept – Stimuli that create our visual experience (what your eyes see, even when you don’t know you see it) Illusion – A percept that fails to agree with real world measurements

31. Two Reasons Illusions Occur in Our Mind: 1.Our mind tries to figure out the most useful aspect of what we are seeing, and sometimes it gets it wrong. (biological failure) Example: Crazy NutsCrazy Nuts

32. Two Reasons Illusions Occur in Our Mind: 2.Our mind tries to cheat by creating a list of common experiences and uses visual stimuli to quickly figure out what experience it matches and how to guide our behavior. (prediction error) Example: Lionel TrainLionel Train

33. Optical Illusions What do you see?

37. Optical Illusions Sometimes, we see objects we recognize, but not how we usually see them. Our mind has no construct in which to place these objects, and we usually call them “junk” or “art”. It may not be until we see them in a different way that we understand their meaning.

38. Shigeo Fukuda Japanese sculptor, died 2009, specialized in optical illusions: Mirror Image

39. Forks, Knives, Gasoline