Psych - Chapter 6 - Summary

Sensation is the detection and direct experience of physical energy as a result of the environment or internal events. Perception is the process by which sensory impulses are organized and interpreted.

Our sensational senses

Sensation begins with the sense receptors, which convert the energy of a stimulus into electrical impulses that travel longer to the brain. Separate sensations can be accounted for by anatomical codes (as set forth by the doctrine of specific nerve energies) and functional code is in the nervous system. In a rare condition called synesthesia, sensation in one modality also he evokes a sensation in another modality, but these experiences are the exception, not the rule.

Psychologist specializing in psychophysics have studied sensory sensitivity by measuring absolute indifference thresholds. Signal- detection theory, however, holds that responses in a detection task consists of both a sensory process in a decision process and will vary with the person's motivation, alertness, and expectations.

Our senses are designed to respond to change in contrast to the environment. When stimulation is unchanging, sensory adaptation occurs. Two little stimulation can cause sensory deprivation. Too much stimulation can cause sensory overload. Selective attention prevents overload and allows us to focus on what is important, but it also deprives us of sensory information we may need, as in inattentional blindness.

Vision

Vision is affected by the wavelength, intensity, and complexity of like, which produces psychological dimensions of visual experience -- hue, brightness, and saturation. The visual receptors, rods and cones, are located in retina of the eye. They sent signals (via other cells) to the ganglion cells and ultimately to the optic nerve, which carries visual information to the brain. Rods are responsible for vision in dim light; cones are responsible for color vision. Dark adaptation occurs in two stages.

Specific aspects of the visual world, such as lines at various orientations, are detected by feature detector cells in the visual areas of the brain. Some of the cells respond maximally too complex patterns. A debate is going on about the possible existence of specialized "face modules" in the brain. In general, however, the brain takes in fragmentary information about wines, angles, shapes, motion, brightness, texture, and other features of what we see and comes up with a unified view of the world.

The trichromatic and opponent- process theories of color vision apply to different stages of processing. In the first stage, three types of cones in the retina respond selectively to different wavelengths of light. In the second, opponent- process sells in the retina and the thalamus respond and opposite fashion to short and long wavelengths of light.

Perception involves the active construction of a model world from moment to moment. The Gestalt principles described the visual strategies used by the brain to perceive forms. Example figure in ground, proximity, closure, similarity, and continuity.

We localize objects in visual space by using binocular and monocular cues to depth. Binocular cues include convergence and retinal disparity. Monocular cues include, among others, interposition and linear perspective. Perceptual consistencies allow us to perceive objects as stable despite changes in the sensory patterns they produce. Perceptual illusions occur when sensory cues are misleading or when we misinterpret cues.

Hearing

Hearing (audition) is affected by the intensity, frequency, and complexity of pressure waves in the air or other transmitting substance, corresponding to the experience of loudness, pitch, and timbre of the sound. The receptors for hearing are hair cels (cilia) embedded in the basilar membrane, located in the organ of Corti and the interior of the cochlea. The sounds we hear are determined by patterns of hair cell movement, which produce different neural codes. When we localize sounds, we use as cues settle differences in how pressure waves reach each of our ears.

Other senses

Taste (gustation) is a chemical sense. Elevations on the tongue called papillae, contain many taste buds. The basic tastes include salty, sour, bitter, sweet, and probably umami. Responses to a particular case depend in part on genetic differences among individuals; for example, some people are super tasters. Taste preferences are also affected by culture and learning, and by the texture, temperature, and smell of food.

Smell (olfaction) is also a chemical scents. No basic editors have been identified, and up to a thousand different receptor types exist. But researchers have discovered that distinct odors activate unique combinations of receptor types, and they have identified some of this combinations. Call toll and individual differences also affects people's responses to particular odors.

The skin senses include touch (pressure), warmth, cold, pain, and variations such as age and tickle. Except in case of pressure, it has been difficult to identify specialized receptors for the senses, but researchers have reported a receptor for one kind of itching and a possible receptor for cold.

Pain is both a can sense and an internal sense. According to the gate- control theory, the experience of pain depends on whether neural impulses get past a "gate" and the spinal cord and reach the brain. According to a revised version of this there he, a matrix of their lawns and the brain can generate pain even in the absence of signals from sensory neurons, which may help explain the puzzling phenomenon of phantom pain. No one theory, however, completely explains perception of pain, which involves the release of many chemicals all along the pain pathways, and also the involvement of glial cells. Pain comes in many varieties, both physiologically and psychologically, and is affected by genetics, expectations, and culture.

Kinesthesis tells us where our body parts are located, and equilibrium tells us the orientation of the body as able. Together, these two senses provide us the feeling of physical embodiment.

Perceptual powers: origins and influences

Many fundamental perceptual skills are inborn or are acquired shortly after birth. By using the visual cliff, for example, psychologists have learned that babies have depth perception by the age of six months and probably even earlier. However, without certain experiences during critical periods early in life, cells of the nervous system deteriorate, change, or fail to form appropriate neural pathways, and perception is impaired. This is why efforts to correct congenital blindness or deafness are most successful when they take place early in life.

Psychological influences on perception include needs, beliefs, emotions, and expectations (which produce perceptual sets). These influences are affected by culture, which gives people practice with certain kinds of experiences and influences what they attend to.

Puzzles are perception

In the laboratory, studies using priming shed that simple visual subliminal messages can influence certain behaviors, judgments, and motivational states, such as thirst. However, there is no evidence that complex behaviors can be altered by "subliminal perception" tapes or similar subliminal techniques.

Extrasensory perception (ESP) refers to paranormal abilities such as telepathy and precognition. Years of research have failed to produce convincing evidence for ESP. Many so-called psychics take advantage of people's desire to believe in ESP, but what they do is no different from the tricks of any good magician. The story of ESP illustrates a central fact about human perception: it does not merely capture objective reality but also reflects our needs, biases, and beliefs.