Sensation and Perception: The Path to Consciousness

1. Chapter 4Sensation & Perception

2. Sensation • The process by which stimulation of a sensory receptor produces neural impulses that the brain interprets as sound, a visual image, an odor, a taste, a pain, or other sensory images. • The registration of information.

3. Perception • A process that makes sensory patterns meaningful.

4. How Do We Interpret Sensations? • STIMULUS - energy that affects what we do. • RECEPTORS – specialized cells that convert environmental energies into signals for the nervous system.

5. The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system:neural impulses. How Does StimulationBecome Sensation?

6. Transduction Transformation of one form of energy into another – especially the transformation of stimulus information into nerve impulses.

7. Sensory pathways – Bundles of neurons that carry information from the sense organs to the brain.

8. Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while. Sensory Adaptation

9. Thresholds • Absolute threshold – Amount of stimulation necessary for a stimulus to be detected. • Difference threshold – Smallest amount by which a stimulus can be changed and the difference be detected (also called just noticeable difference – JND).

10. Approximate absolute thresholds for the 5 senses: • Vision - Candle flame seen at 30 miles on a clear, dark night. • Hearing - Tick of a watch under quiet conditions at 20 feet. • Taste - 1 Teaspoon of sugar in 2 gallons of water. • Smell - 1 Drop of perfume diffused into a three-room apartment. • Touch - A bee's wing falling on your cheek from 1 centimeter above.

11. Weber’s law The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low. Thresholds

12. Signal Detection Theory • Signal detection theory – Perceptual judgment as a combination of sensation and decision-making processes. Stimulus event Neural activity Comparison with personal standard Action (or no action)

13. Studies have found that subliminal words flashed briefly on a screen can “prime” a person’s later responses. No controlled research has ever shown that subliminal messages delivered to a mass audience can influence people’s buying habits. Subliminal Persuasion

15. THE EYE Video

16. PUPIL – an adjustable opening in the eye through which light enters. IRIS – the colored structure on the surface of the eye. The Structure of the EYE

17. CORNEA – a rigid transparent structure on the outer surface of the eyeball. LENS – a flexible structure that can vary in thickness, enabling the eye to accommodate. The Structure of the EYE

18. RETINA – a layer of visual receptors covering the back surface of the eyeball. The Structure of the EYE

19. Retina: Visual Sensation Photoreceptors– Light-sensitive cells in the retina that convert light energy to neural impulses. Rods–Sensitive to dimlight but not colors. Cones–Sensitive tocolors but not dim light. Fovea – Area of sharpest vision in the retina.

20. Visual Receptors • Cones • color vision • daytime • detailed • 5-10% of visual receptors in the retina are cones • 7 million

21. Visual Receptors • Rods • night vision • black and white • 125 million

22. Interactive

23. The Visual Pathway Optic nerve – Bundle of neurons that carries visual information from the retina to the brain.

24. The Visual Pathway • Blind spot – The point where the optic nerve exits the eye and where there are no photoreceptors. DO IT YOURSELF! page 122

25. Review from Chapter 3!!! In which area of the brain are visual signals processed???

26. Answer: • VISUAL CORTEX Part of the brain in the occipital lobe where visual sensations are processed.

27. Neural Pathways in the Human Visual System

28. How the Visual System Creates Color • Electromagnetic spectrum – Entire range of electromagnetic energy, including radio waves, X-rays, and visible light. • Visible spectrum – Tiny part of the electromagnetic spectrum to which our eyes are sensitive.

29. How the Visual System Creates Brightness Wavelength Intensity (amplitude) Color Brightness

30. Trichromatic Theory • The idea that colors are sensed by 3 different types of cones; explains the earliest stage of color sensation. • Blue • Green • Red

31. Opponent-Process Theory • We perceive color not in terms of independent colors but in terms of a system of paired opposites. • Red vs. Green • Yellow vs. Blue • White vs. Black

32. Afterimages • Sensations that linger after the stimulus is removed. • Most often called negative afterimages • Try the activity on page 121

33. Color Blindness • Vision disorder that prevents an individual from discriminating certain colors.

34. Red-Green Colorblindness • Difficulty distinguishing red from green and either red or green from yellow.

35. The Camera • When you look at an object, light rays are reflected from the object and enter the eye through the pupil.  • The light rays are bent, refracted and focused by the lens. The lens' job is to make sure the rays come to a sharp focus on the retina. The resulting image on the retina is upside-down.  • Here at the retina, the light rays are converted to electrical impulses which are then transmitted through the opticnerve, to the brain, where the image is translated and perceived in an upright position!

36. Hearing

37. High Amplitude Low Amplitude Hearing • The Physics of Sound Amplitude – Physical strength of a wave.

38. Low Frequency High Frequency Hearing • The Physics of Sound Frequency – Number of cycles completed by a wave in a given amount of time, usually a second.

39. Hearing • Hertz (Hz) – unit of frequency representing one cycle (vibration) per second.

41. Tympanic membrane –The eardrum How Sound Waves Become Auditory Sensations

42. Cochlea –Where sound waves are transduced How Sound Waves Become Auditory Sensations

43. Basilar membrane –Thin strip of tissue sensitive to vibrations How Sound Waves Become Auditory Sensations Cochlea

44. Auditory nerve –Neural pathway connecting the ear and the brain How Sound Waves Become Auditory Sensations

45. Review from Chapter 3!!! In which area of the brain are auditory signals processed???

46. Answer: • Auditory cortex – Portion of the temporal lobe that processes sounds.

48. ANSWERS • (a) outer ear (pinna)   • (b) ear canal    • (c) eardrum • (d) hammer, anvil, and stirrup    • (e) cochlea    • (f) auditory nerve

49. The Psychology of… • Pitch – Sensory characteristic of sound produced by the frequency of the sound wave. • Loudness – Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave. • Timbre– Quality of a sound wave that derives from the wave’s complexity. Video Clip

50. Hearing Loss • Conduction Deafness – An inability to hear resulting from damage to structures of the middle or inner ear.