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Notes on Vision - Psychology: Science and Practice | PSY 110, Study notes of Psychology

Wright State University (WSU) - DaytonPsychology
Prof. Robert Gordon

Material Type: Notes; Professor: Gordon; Class: HON: Psy: Science & Practice; Subject: Psychology; University: Wright State University-Main Campus; Term: Fall 2006;

Typology: Study notes

Pre 2010

Uploaded on 08/19/2009

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1Psychology 110
Dr. Gordon
Module #12
“Vision”
2A. Vision
•1. The properties of light energy
•2. The eye
•3. Visual processing pathways
•4. Feature detection
•5. Color perception
31. Properties of light energy
•The cartoon to the left reminds us how much the “eye” dominates our sensory and perceptual experience. In
this module, we will examine the anatomy of the eye, visual processing, color perception and constancy.
41. Properties of light energy
•The slide to the left illustrates the spectrum of electromagnetic energy. White light energy is a form of
electromagnetic radiation that travels as a wave, moving naturally at the speed of light. Other forms of
energy are not visible to the human eye.
51. Properties of light energy
•The slide above illustrates how a human being and bee perceive the same flower. A bee can only detect
ultraviolet waves. In contrast, the human eye is sensitive to the visible light spectrum and therefore sees a
yellow flower. Reptiles and fish can perceive longer wavelengths like in the infrared spectrum.
61. Properties of light energy
•A light wave will vary according to its amplitude (height or brightness) and wavelength (the distance
between the peaks of the waves or the perception of color). Typically, when we perceive color, we actually
perceive a mixture of colors. Light can also vary in its purity.
72. The eye
•Let’s turn our attention to the anatomy of the eye. Some of the visual structures to be discussed include the
cornea, pupil, iris, lens, the retina, and fovea.
82. The eye
•The cornea is a protective covering that shields the eye (i.e., It is like a plexiglass). The pupil and iris
regulate the amount of light that can penetrate the rear of the eye.
92. The eye
•The iris or the color of the eye is actually a muscle that contracts given the amount of light in the
environment. The lens is a transparent eye structure that focuses the light rays on the retina. The lens can
remind one of a soft contact lens.
10 2. The eye
•The lens is “jelly like” and changes its shape depending on how far away objects are from the viewer.
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Download Notes on Vision - Psychology: Science and Practice | PSY 110 and more Study notes Psychology in PDF only on Docsity!

1 Psychology 110

Dr. Gordon

Module

“Vision”

2 A. Vision

• 1. The properties of light energy

• 2. The eye

• 3. Visual processing pathways

• 4. Feature detection

• 5. Color perception

3 1. Properties of light energy

  • The cartoon to the left reminds us how much the “eye” dominates our sensory and perceptual experience. In this module, we will examine the anatomy of the eye, visual processing, color perception and constancy.

4 1. Properties of light energy

  • The slide to the left illustrates the spectrum of electromagnetic energy. White light energy is a form of electromagnetic radiation that travels as a wave, moving naturally at the speed of light. Other forms of energy are not visible to the human eye.

5 1. Properties of light energy

  • The slide above illustrates how a human being and bee perceive the same flower. A bee can only detect ultraviolet waves. In contrast, the human eye is sensitive to the visible light spectrum and therefore sees a yellow flower. Reptiles and fish can perceive longer wavelengths like in the infrared spectrum.

6 1. Properties of light energy

  • A light wave will vary according to its amplitude (height or brightness) and wavelength (the distance between the peaks of the waves or the perception of color). Typically, when we perceive color, we actually perceive a mixture of colors. Light can also vary in its purity.

7 2. The eye

  • Let’s turn our attention to the anatomy of the eye. Some of the visual structures to be discussed include the cornea, pupil, iris, lens, the retina, and fovea.

8 2. The eye

  • The cornea is a protective covering that shields the eye (i.e., It is like a plexiglass). The pupil and iris regulate the amount of light that can penetrate the rear of the eye.

9 2. The eye

  • The iris or the color of the eye is actually a muscle that contracts given the amount of light in the environment. The lens is a transparent eye structure that focuses the light rays on the retina. The lens can remind one of a soft contact lens.

10 2. The eye

  • The lens is “jelly like” and changes its shape depending on how far away objects are from the viewer.

Accommodation is the process in which lens adjusts to the distance of objects. Accommodation problems come in the form of nearsightedness (close objects are seen clearly but distant objects appear blurry) and farsightedness (distant objects are seen clearly but close up objects are not).

11 2. The eye

  • Let’s take a closer look at farsightedness and nearsightedness. Nearsightedness refers to when “…light rays from distant objects focus in front of the retina. When their image reaches the retina, the rays are spreading out, blurring the image.” In contrast, farsightedness occurs when “light rays from nearby objects come into focus behind the retina, resulting in blurred images.”

12 2. The eye

  • Let’s move on to one of the most important structures of the eye, the retina. The retina is “rich” neural tissue that lines the surface at the back of the eye. It absorbs light, processes images, and transmits neural signals to visual cortex of the cerebrum.

13 2. The eye

  • The retina is unique because it is an extension of the brain. The retina is a thin lining of neural tissue.

14 2. The eye

  • It is a very sensitive piece of visual “hardware” because it contains important visual receptors (rods, cones, bipolar cells, etc..) and axons that run through a hole called the optic disk.

15 2. The eye

  • Bipolar and ganglion cells assist in the transmission of neural messages to the optic nerve. We can think of these cells as filters.

16 2. The eye

  • At the back of the eye, there is a hole called the blind spot. That is, where the optic nerve leaves the eye, there are no visual receptors. The optic disk is the location where axons converge to form the optic nerve.

17 2. The eye

  • Let’s turn our attention now to some of the functional units of the retina starting with the rods and cones the retina serves three functions. First, the conversion of light energy to neural impulses is the primary function of the rods and cones. Second, rod and cone receptors help one adapt to changes in environmental light intensities or what is termed dark and light adaptation. Third, the retina is instrumental in processing or filtering information before it gets to the brain. This is called lateral antagonism.

18 2. The eye

  • These are actual photographs of rods and cones. First, rods are specialized visual receptors that play critical role in night and peripheral vision. Rods are more sensitive than cones to dim light. Since a greater number of rods are located in the periphery of the retinal lining, it is not surprising that rods are also responsible for peripheral vision.

19 2. The eye

  • Cones are specialized visual receptors that play a key role in daylight vision and color vision. Cones provide visual acuity (perceived sharpness and precise detail). Cones are in higher concentration at the center of the retina. At the fovea, a small spot in the center of the retina, contains all cones.

20 2. The eye

31 5. Color perception

  • The opponent process theory suggests that the color receptors work in pairs and are antagonistic (yellow- blue, black-white, and red-green). In theory, colors are signaled in pairs by neurons that fire faster color and slower to another color.

32 5. Color perception

  • A real life example of the opponent process occurs when exposed to a flash bulb of a specific color, one sees spots of the other color. For example, if a blue flash is used, one is likely to see yellow spots. The yellow spots are called afterimages. An afterimage refers to a visual image that persists after a stimulus is removed. Let’s try an afterimage exercise.

37 5. Color perception

  • Color perception researchers have concluded that both theories are supported. It might be that color sensitive cones account for trichromatic theory as illustrated below. In contrast, opponent process theory suggests that color perception is processed later in the visual cortex, thalamus and some of the ganglion cells in the retina.