Sensation and Perception

1. Sensation and Perception

2. Objectives Identify the senses Define sensation and perception Describe the structure of the eye and the mechanism of seeing and perception Explain the theory behind magic eye pictures.

3. Sensation We have all heard about our senses. Have we? How many senses do we have. Write down as many senses as you can think of�

4. How many senses? Most people stop at FIVE Vision, Hearing, Touch, Taste, Smell Current thinking includes another sense � Kinesthaesia � a sense of balance or position.

5. The Sixth Sense? Psychologists study the possible existence of a paranormal sense At the moment, it is considered uncertain. At Edinburgh University, the Centre for Parapsychology collects reports from all over the world and investigates them. A bit like Scully and Mulder but in real life.

6. The Sixth Sense Edinburgh have found that all but about 0.1% could be explained by existing theory. A very high proportion were shown to be fraudulent. The 0.1% remaining� Edinburgh say they can�t be explained� YET!

7. Visual Perception Sensation: the physical stimulation of the sensory receptors Perception: the process of interpreting and understanding sensory information What happens when sensation and perception go wrong?

8. Breakdown in perception and sensation Anaesthetic � e.g. Epidural during childbirth Sensory stimulation is definitely taking place, but no perception of pain. Schizophrenia � e.g. auditory illusions The voices are real enough, but sensory stimulation is not taking place.

10. The Retina Consists of nerve endings Rods � named because of their shape � are most sensitive but only black & white Cones � sensitive to colour

11. The Blind Spot Test for your blind spot using the handout. The explanation is that our mind tries to �fill in� the missing field of vision caused by the blind spot. It makes the best guess, based on the background. But it may be disastrous�.

14. Three Dimensions The image on the retina is in two dimensions (just like a photograph) And yet we see in three dimensions � we do exist in a solid world after all! How can we perceive distance and dimensions?

15. Convergence Try the pencil test Focus on the pencil and as you move it towards you � still in focus, you should feel the muscles in your eye protesting!! By storing the muscular position for focus at a particular distance, the mind can determine the distance of an object.

18. Retinal Disparity Another pencil test. Hold the pencil in front of you. Close one eye, open it, then close the other. What do you notice?

19. Disparity You get two views of the pencil Just as you get two views of the man in the picture

20. 3D perception If we can superimpose the images from each eye, our mind will smooth off the image and what we see will appear in three dimensions.

21. Stereoscopic vision This is the principle behind the stereoscope

22. And also behind Magic Eye Pictures