Ch. 5 – Sensory, Attentional and Perceptual Processes
1 Explain the functional limitations of sense organs.
Ans. Our sense organs function with certain limitations. E.g. our eyes cannot see things which are very bright or dim. Our senses function within a limited range of stimulation. In order to be noticed by the sensory receptor, a stimulus needs to be of a suitable intensity to be noticed by the sensory receptor, i.e. it has to carry a minimum value or weight. The minimum value of a stimulus required to activate a given sensory system is called absolute threshold or absolute limen. E.g. the minimum number of sugar granules required to say that water in a glass is sweet will be the AL of sweetness. The AL varies according to individuals and situations. Hence, the number of sugar granules that may produce the experience of ‘sweetness’ in 50 percent of occasions will be called the AL of sweetness. Also, in order to notice two stimuli as different from each other, there has to be some minimum difference between the values of those stimuli. The smallest difference in the value of two stimuli that is necessary to notice them as different is called difference threshold or difference limen (DL). The DL is the minimum amount of change in a physical stimulus that is capable of producing a sensation difference in 50 percent of the trials.
2 What is meant by light and dark adaptation? How do they take place? Ans. The process of getting adjusted to different intensities of light is called ‘visual adapatation’. Light adaptation refers to the process of adjusting to bright light after exposure dim light. Dark adaptation refers to the process of adjusting to dimly illuminated environment after exposure to bright light.
Process of visual adaptation:
Visual adaptation occurs due to certain photochemical processes. The rods have a photo-sensitive chemical substance called rhodopsin. When light causes the molecules of this substance to break down, light...
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