Perception – is a cognitive psychic process of reflexion of objects and phenomena of real world in the human brain, in the whole complex of their qualities and characteristics.

Sensation is a cognitive psychic process of reflexion of objects’ and phenomena separate properties in human brain at their direct impact on human sense-organs.

Perception – is a cognitive psychic process of reflexion of objects and phenomena of real world in the human brain, in the whole complex of their qualities and characteristics.

Sensation is the simplest psychic process, primary orientation form of the living organism in the environment. Sense organs are the only channels, through which outer world penetrates into human consciousness. Positive or negative emotional coloring is typical to sensations. Pleasant or unpleasant sensations signal about positive or negative effect of stimuli (irritant) and cause corresponding effect on it.

According to I.Setchenov and I.Pavlov, sensations are the original reflex actions, the physiological basis of which state nervous processes which are caused by irritants as a result of their influence on sense-organs or analyzers.

Analyzers are the organs, which analyze surrounding reality, for example visual analyzer singles out light energy, or fluctuations of the electromagnetic waves; an auditory one – sounds (or air fluctuations), gustatory and olfactory ones – chemical properties of substances; skin analyzer – mechanical properties of objects and phenomena that cause different sensation. Every analyzer has the peripheral analyzing part, or receptor, that is sense-organ, (which task is to single out light, sound, smell and so on), its other part is the leading way (path) from the receptor to the central part of analyzer, located in the brain.

A basic problem for any sensory system is its ability to detect varying degree of energy in the environment. This energy can take the form of light, sound, chemical or mechanical stimulation. How much of the stimulus is necessary to us to see, hear, taste, smell or feel something? One way to answer these questions is to assume that each of us has absolute threshold or minimum amount of energy that we can detect. When a stimulus has less energy than this absolute threshold, we cannot detect its presence, when the stimulus has more energy than the absolute threshold, we can detect the stimulus.

Approximate absolute thresholds for 5 senses

Vision – a candle flame at 30 miles on a dark, clear night

Hearing – a ticking watch at 20 feet under quiet conditions

Taste - a teaspoon of sugar in 2 gallons of water

Smell – one drop of perfume diffused through out 3 rooms

Touch – the wing of a fly falling on your cheek from a distance of 1 centimeter

Signal detection theory is the theory that sensitivity to sensory stimuli depends on a variety of factors besides the physical intensity of the stimulus and the sensory abilities of the observer. These factors include individual and contextual variations such as fatigue, expectancy, and the urgency of the moment. Let’s consider the case of two air traffic controllers with exactly the same sensory ability to detect blips on a radar screen. One is monitoring the radar screen while working overtime late into the night and is feeling fatigued. The other is watching the screen in the morning after having a good night sleep. The fatigued radar operator fails to see a blip indicated that the small private plane is flying too close to a large passenger jet, and the two collide. However, in the similar situation, the well-rested controller detects a private plane and asks a private plane’s pilot to change course.

2. Classification and types of sensation.

Depending on the interaction of sense-organs with stimuli/irritants we can distinguish: 1) contact (tactile, gustatory, pain) and 2) distant (visual, auditory, olfactory) sensations.

Depending on location of receptors in organism – on the surface, inside the body, in the muscles and tendons (сухожилие) – there are such types, as: 1) exterioceptive sensations, 2) interioceptive sensations; 3) proprioceptive sensations; 4) temperature sensations.

The eye is the organ of vision sensations. To understand the sense of vision, we need to know some basic facts about light, the energy that makes vision possible. Light is a form of electromagnetic energy that can be described in terms of wavelength. The wavelength is the distance from the peak of one wave to the peak of the next. Visible light’s wavelength range from about 400 to 700 nanometers. The difference between visible light and other forms of electromagnetic energy is its wavelength. Outside the range of visible light are longer radio and infrared waves, and shorter ultraviolet and X rays. This other wavelengths continually bombard us, but we do not see them.

One can distinguish a light refraction (cornea, pupil) and light sensitive (retina with its cones sensitive to daylight and rods, sensitive to darkness) part in eye.

The ear is the organ of hearing sensations. Sounds, or sound waves, are vibrations in the air that are processed by our auditory (or hearing) system. The sound wave’s amplitude is measured in decibels (dB), the amount of pressure produced by a sound wave relative to a standard; the typical standard is the weakest sound the human ear can detect. Thus, zero decibels would be the softest noise detectable by humans. Noise rated at 80 decibels or higher, if heard for prolonged periods of time, can cause permanent hearing loss. A quiet library is about 40 decibels, conversation – 60 decibels, a car horn about 90 decibels, a rock band at close range 120 decibels, a rocket launching – 180 decibels. Noise levels have risen in recent years.

Loudness – is the perception of sound waves amplitude. In general, the higher the amplitude of the sound wave, the louder the sound is perceived to be. In the world of amplitude, this means that air is moving rapidly for loud sounds and slowly for soft sounds.

Nose is one of the organs of olfactory sensations. Our nose has 2 cavities or open spaces inside it. The roof of each of these nasal cavities is lined with a thick covering called the olfactory membrane, which is really a type of skin. Covering the olfactory membrane is a thin layer of mucus. Embedded in the membrane itself are millions of receptor cells called olfactory rods.

The stimuli that excite our olfactory rods are complex chemicals in gaseous form that are suspended in the air we breathe. As air pass over the olfactory membrane, some of the complex chemicals in the air are absorbed into the mucus. These gaseous molecules appear to lock onto specific receptor sites on the cilia. This “locking on” causes the olfactory rods to fire off an input message to our brain.

Smell qualities. John Amoore (University of California) divided seven primary smell qualities: 1) camphor; 2) musky; 3) floral (roses); 4) peppermint; 5) ethereal (dry-cleaning fluid); 6) pungent/едкий (vinegar); 7) putrid/гнилой (rotten eggs).

Smell is a unique sense in at least two important ways. First, it is perhaps the most ancient sense at all. Single-celled organisms could detect molecules in the water around them long before they became sensitive to sights or sounds. Second, smell seems more directly related to emotion and motivation than the other senses. Sensory inputs from our skin, eyes and ears pass through the thalamus and are relayed directly to our cortex. However, the olfactory nerve mostly bypasses the thalamus and runs directly to those sub-centers of the brain that process emotions, not thoughts.

According to William Cane, women appear to be superior to men at such tasks as identifying and remembering smells. According to Richard Porter study each person has a characteristic and unique “odor signature”. In one of his studies mothers of newborn infants could correctly identify their child’s clothes by smell alone. Mothers don’t lose this ability as their children grow up, either. In another research 17 of 18 mothers tested could, by smell alone, pick out the T-shirt worn by their 3 to 8-years old child. And 16 out of 18 parents with 2 children could tell which T-shirt was worn by which child.

The organs of gustatory/taste sensation – taste receptors are situated on the tongue and palate. There are about 10,000 taste buds in our mouth, each made up of several receptor cells. There are four basic taste qualities: sweet, bitter, sour, salty. Gustatory sensations are strongest and clearest when integrated with olfactory sensations.

Fig. 10-1. The distribution of gustatory papillae, their innervation, and the regions of maximum sensitivity to different submodalities of taste on the human tongue. (Altner H: Physiology of taste. In Schmidt RF [ed]: Fundamentals of Sensory Physiology. New York, Springer-Verlag, 1978)

Taking its name from Japanese, umami is a pleasant savoury taste imparted by glutamate, a type of amino acid, and ribonucleotides, including inosinate and guanylate, which occur naturally in many foods including meat, fish, vegetables and dairy products. As the taste of umami itself is subtle and blends well with other tastes to expand and round out flavours, most people don't recognize umami when they encounter it, but it plays an important role making food taste delicious.

Дата добавления: 2015-10-24