Experiencing Sensory Adaptation
Speaking about sensory adaptation it is important to refer to such notions as sensation and perception, which can be regarded as a background of the outside world embracement by individuals. Both of these processes are predetermined by a definite stimuli influencing the senses and sending it to the brain. In case with sensation, the information, which is sensed through vision, hearing, smell, taste, spatial orientation, is usually converted by the receptors into neuron impulses and transmitted to the brain. Afterwards the process of perception, when the brain actively organizes and interprets the gathered information, ensues (Heffner, 2001). Nevertheless, the stimulus, which affects the organism, is not always perceived in the same way. Firstly, there exists the threshold, which makes changes in a stimulus noticeable to a person. Secondly, the impact of the same stimulus during some definite time causes the sensory adaptation, which means that the receptors get accustomed to stimulus and lose their sensitivity to it. The sensory adaptation has been a peculiar feature for the individuals through the evolution. According to Schaffner it is a systematic interaction between the environmental and phenotypic output (Schaffner, 2009). Moreover, it is efficient for the reproductive and surviving functions of human representatives as “positive natural selection is the driving force behind adaptive evolution”(Schaffner, 2009).
Having conducted the experiments mentioned in the task one can find the examples of the sensory adaptations, which can be met in every-day life. The first experiment, which was held, was rubbing the index fingers gently over a coarse sand paper a few times. Consequently, the sensation of the paper coarseness was felt very strongly and can be rated as 7 (very coarse) in the beginning. The same action conducted in a minute caused a less distinctive feeling of the surface coarseness, which can be rated as 5 according to the rate from one to 7. Therefore, the fingers became less sensitive to the coarseness, and to some extend adapted to the given stimulus. Obviously, according to the description of the tactile sensory system offered by Murray it is possible to explain that the information that was carried from a tactile sense receptor to the neuronal axons was finally received through the Somatosensory Cortex by CNS (Murray 2009).
During the second experiment, when the sugar water was put into the mouth and swished in it, the perception of the water taste became less sweet after some time, which means that the receptors got used to the taste and, finally, the adaptation of taste receptors took place. After having tasted the fresh water in several seconds its taste was perceived as salty. Therefore, when explaining the result of the experiment, it is important to pay attention to the structure of the tongue and that there are different sorts of papillae on it, which response for different kinds of tastes perception (Wood, 2006). Consequently, the adaptation of the taste sensory receptors, which were important for sweet and salty taste detection led to the depicted results of the experiments.
In the third experiment, where 15 index cards where placed over the beam of light in a dark room, the vision adaptation was observed. At first, after the cards were removed one by one a blurry spot was observed in the middle of 8 cards, which were left. After a few minutes the light began to look more brightly, but after repeating the same process of adding cards over a 15-minute period the dim light started increasing. The system of vision adaptation to darkness and light is connected with the existence of cones and rods in the human eye. While the cones can adapt to the light shift very quickly, the rods become more sensitive much slower (Wood, 2006).
The fourth experiment with different temperatures of the water in bawls is the example of the adaptation of the temperature receptors, which are placed under the skin. The receptors of the hand, which was in the hot water were adapted to the hot temperature, therefore, the lukewarm water seemed to be colder. At the same time the receptors of the second hand were stimulated by the cold temperature, which caused the perception of lukewarm water as warmer than it really was.
Having conducted four different experiments connected with sensory adaptation one can see, that all sensory systems can be exposed to the adaptation, when the receptors are disposed to the influence of the same stimulus for a definite period of time. As a result, learning the functions of the nervous system and of sensory systems of the individuals is important for understanding human behavior and psychology.