For instance, if you misplaced your keys, how would you look for them? If you had a yellow key fob, you would probably look for yellowness of a certain size in specific locations, such as on the counter, coffee table, and other similar places. You would not look bidet converter kit for yellowness on your ceiling fan, because you know keys are not normally lying on top of a ceiling fan. That act of searching for a certain size of yellowness in some locations and not others would be top-down—under your control and based on your experience.
Absolute threshold refers to the minimum amount of stimulus energy that must be present for the stimulus to be detected 50% of the time. Another way to think about this is by asking how dim can a light be or how soft can a sound be and still be detected half of the time. The sensitivity of our sensory receptors can be quite amazing. It has been estimated that on a clear night, the most sensitive sensory cells in the back of the eye can detect a candle flame 30 miles away (Okawa & Sampath, 2007). Under quiet conditions, the hair cells can detect the tick of a clock 20 feet away .
Think about how tastes are blunted and sometimes different when your sense of smell is disrupted due to a cold. The trichromatic theory asserts that three distinct cone groups are tuned to slightly different wavelengths of light, and it is the combination of activity across these cone types that results in our perception of all the colors we see. The opponent-process theory of color vision asserts that color is processed in opponent pairs and accounts for the interesting phenomenon of a negative afterimage. We perceive depth through a combination of monocular and binocular depth cues. The place theory of pitch perception suggests that different portions of the basilar membrane are sensitive to sounds of different frequencies. More specifically, the base of the basilar membrane responds best to high frequencies and the tip of the basilar membrane responds best to low frequencies.
She had complained frequently that I was bad at matching my shirts, pants, and ties, but this time, she sounded especially alarmed. As a single father with no one else to ask at home, I drove us to the nearest convenience store and asked the store clerk if my clothes matched. She said my pants were a bright green color, my shirt was a reddish-orange, and my tie was brown.
That signal triggers the perception of the fatty acids and probably stirs other physiological reactions. CD36 is also found in other parts of the digestive system, playing a role in fat absorption in the intestines and digestion in the stomach, adding to the complexity of the relationship between the protein and fatty acids. The outer ear includes the pinna, which is the visible part of the ear that protrudes from our heads, the auditory canal, and the tympanic membrane, or eardrum. The middle ear contains three tiny bones known as the ossicles, which are named the malleus , incus , and the stapes .
The olfactory system creates an image for the mixture and stores it in memory just as it does for the odor of a single molecule . At present, however, there is no clinical test for umami taste, even though tests for the other four basic tastes have been widely used in quantitative gustometry. We have developed a new method to clinically assess the sensitivity of umami taste using a filter paper disc with monosodium glutamate as the prototype umami substance. We found that some elderly patients complained only of the loss of umami taste sensation, whereas the sensation of the other four basic tastes was normal. Those patients without normal umami taste sensitivity were all over 65 years old, and complained of appetite and weight loss, resulting in poor general health.
The optic nerve from each eye merges just below the brain at a point called the optic chiasm. As Figure5.12 shows, the optic chiasm is an X-shaped structure that sits just below the cerebral cortex at the front of the brain. At the point of the optic chiasm, information from the right visual field is sent to the left side of the brain, and information from the left visual field is sent to the right side of the brain. AsFigure 5.25shows, our perception can vary tremendously, depending on what is perceived as figure and what is perceived as ground. Stare at the white dot for 30–60 seconds and then move your eyes to a blank piece of white paper.
For a single molecule, the pattern of activation across the glomeruli paints a picture of the chemical structure of the molecule. Thus, the olfactory system can identify a vast array of chemicals present in the environment. Most of the odors we encounter are actually mixtures of chemicals (e.g., bacon odor).