D the difference threshold the difference threshold

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than subliminal attempts to sneak into our subconscious mind.  D. The Difference Threshold - - The difference threshold is defined as the smallest difference between two stimuli that people can  perceive 50 percent of the time. (Just noticeable difference)  - Weber’s law states that the difference threshold, or jnd, is directly proportional to the magnitude of the  stimulus with which the comparison is being made and can be expressed as a Weber fraction.  Example, two objects, if the weight were 500 grams, a second weight would have to be at least 510  grams for you to discriminate between them. 500+500*1/50 = 510  E. Sensory Adaption - Sensory systems  are finely attuned to changes in stimulation. Sensory neurons are engineered to respond  to constant stimulus by decreasing their activity, and the diminishing sensitivity to an unchanging  stimulus is called  sensory adaptation - Adaptation  occurs in all sensory modalities. Although it may reduce sensitivity, it is adaptive, for it  frees our senses from the constant and the mundane, allowing them to pick up informative changes in the  environment.  III. The Sensory System - Transduction is the process whereby the characteristics of a stimulus are converted into nerve impulses.  A. Vision - The normal stimulus for vision is electromagnetic energy, light waves, which are measured in  nanometers (nm), or one billionth of a meter. (700nm-400 nm) i) The Human Eye Cornea , a transparent protective structure at the front of the eye. Pupil , an adjustable opening that can dilate or constrict to control the amount of light that enters the  eye, and the size is controlled by muscles in the colored  iris  that surrounds the pupil.  Lens,  an elastic structure that becomes thinner to focus on distant object and thicker to focus on  nearby objects Retina , a multilayered light-sensitive tissue at the rear of the fluid-filled eyeball.  The ability to see clearly depends on the  lens ’s ability to focus the image directly onto the  retina.   a) Myopia – nearsightedness A blurred image for faraway objects. Eyeball is longer than normal  b) Hyperopia – farsightedness Occurs when the lens does not thicken enough and the image is therefore focused on a  point behind the retina.  ii) Photoreceptors: The Rods and Cones The retina is an extension of the brain, and it contains two types of light-sensitive receptors: rods,  and cones.  a) Rods:  which function best in dim light, are primarily black-and-white brightness receptor.  b) Cones : which are color receptors, function best in bright illumination. 
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c) Fovea : a small area in the center of the retina that  contains no rods
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  • Fall '07
  • Psychology, nerve impulses

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