© 2011 The McGraw-Hill Companies, Inc. Instructor name Class Title, Term/Semester, Year Institution Introductory Psychology Concepts Vision

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 2 Light energy. Of the full spectrum of electromagnetic radiation, only the narrow band between 400 and 700 nanometers (nm) is visible to the human eye. One nanometer equals one 1,000,000,000th of a meter. Vision Interpretation of the electromagnetic spectrum in terms of amplitude and wavelength

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 3 Visible Light. + The lowest visible frequency is called red, the highest is violet. + White light is an even distribution of all visible light. + Black is the absence of light. Hue, Saturation, and Brightness. + Hue is the actual color. It is measured in angular degrees counter-clockwise around the cone starting and ending at red=0 or Saturation is the purity of color, measured in percentage from the center of the cone (0) to the surface (100). + Brightness is measured in percent from black (0) to white (100). Source: Vision Light, color (hue), brightness, and saturation

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 4 Lens Ciliary muscles Pupil Cornea Iris Fovea Optic nerve to the brain Blind spot (optic disk) { Retina Vision Parts of the eye

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 5 The iris regulates the size of the pupil. Lens Ciliary muscles Pupil Cornea Iris Fovea Optic nerve to the brain Blind spot (optic disk) { Retina Vision Parts of the eye

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 6 Optic nerve to the brain Lens Ciliary muscles Pupil Cornea Iris Fovea Blind spot (optic disk) { Retina Vision Parts of the eye

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 7 The retina contains the rod and cone photoreceptor cells. Lens Ciliary muscles Pupil Cornea Iris Retina Fovea Blind spot (optic disk) { Optic nerve to the brain Vision Parts of the eye

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 8 The image entering the eye is reversed by the lens and cast on the retina. Lens Ciliary muscles Pupil Cornea Iris Fovea Blind spot (optic disk) { Optic nerve to the brain Retina Vision Parts of the eye

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 9 The optic disk, where the optic nerve exits the eye, has no receptors and produces a blind spot, as demonstrated in the enlarged view below. Ganglion cells Amacrine cells Bipolar cells Horizontal cells ConeRod Light Optic nerve fibers (to brain) Back of eye Ganglion cell layer Bipolar cell layer Photoreceptor layer Blind spot (optic disk) Vision Parts of the eye

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 10 The Young-Helmholtz trichromatic theory proposed three different receptors, one for blue, one for green, one for red. The ratio of activity in the three types of cones yields our experience of a particular hue, or color. Vision Two classic theories of color vision: 1: Young-Helmholtz trichromatic theory (three types of cones)

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 11 Hering’s opponent-process theory also assumed that there are three different receptors: one for blue-yellow, one for red-green, one for black-white. Each of the receptors can function in two possible ways, depending on the wavelength of the stimulus. Again, the pattern of activity in the receptor yields our perception of the hue. Vision Two classic theories of color vision: 2: Hering’s opponent-process theory (red-green and blue-yellow cones)

© 2011 The McGraw-Hill Companies, Inc. Introductory Psychology Concepts: Vision 12 These dotted figures are used to test for color-deficient vision. The left one tests for blue-yellow color blindness, the right one for red-green color blindness. Because the dots in the picture are of equal brightness, color is the only available cue for perceiving the numbers in the circles. Vision Color Blindness + Trichromats: people with normal color vision + Dichromats: deficient in the blue-yellow system, the red-green system, or both. (Approximately 7% of the male population and 1% of the female population are dichromats.) + Monochromats: sensitive only to the black-white system, totally color-blind.