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Sensation refers to the activation of the sense organs.

For it an stimuli is required to be present in the environment.

  • An stimuli is an agent or some thing that causes a response, or considered to be causing a response.

  • The study of the relationship between the physical aspects of the stimuli and our psychological experience of them is called Psychophysics.


  • We rely on the senses in order to experience the world around us and to adapt to our environment.

Human beings possess at least 10 sensory channels. Each sense provides a channel through which information received from the world is transmitted to the brain


  • Vision is perhaps the most important and most often-used sense , and it has been suggested that we obtain three-quarters of our information about the world through sight.

  • For example, human being are blind to ultra-violet light , but honey-bees and ants can see it. Likewise, human beings cannot perceive infra-red radiations either by vision or touch, because it lies between light and heat, but rattlesnakes are sensitive to it


  • The eye encodes the information it receives through electromagnetic radiations (light) into a form that the human nervous system can use.
  • The retina the black of the eye transform the light energy into electro-chemical energy; this manifests itself as COLOR PERCEPTION
  • an impulse in the group of nerves running from the eye to the brain(called the optic nerve)


  • A number of workplace problems with abnormal color vision have been identified , such as inefficiency, financial loss, personal embarrassment , and danger(voke,1982).
  • It is said that 6% of males and 0.55% of females have a deficiency when it comes to discriminating between colors. (oborne,1995) but very few people are color blind.


  • Light has to be evenly distributed , otherwise glare will result , causing discomfort , visual fatigue , and accidents .
  • Glare is caused by a marked contrast in brightness between two surfaces.

In glare , another issue to consider is visual flicker. Instead of our eyes coming into contact with a stimulus in the form of a stable light or illumination, we counter the light that flickers


  • The physical stimulus for hearing is pressure waves in the air.
  • Sounds that human beings can hear range from 20Hz to 20,000Hz.
  • Tonal quality enables us to distinguish different musical instruments and voices.


  • Smell and Taste
  • Skin based senses





The other two senses are Kinesthetic and Vestibular sense.


What is attention ?

Attention is the focusing on one thing while ignoring other things that may be going on at the same time. 

  • If you are able to continue reading a book without being distracted by children running and screaming around you, and a dog is barking then you’re maintaining your attending the book.
  • If the dog finally bites your ankle, ( ) your attention would shift from the book and may become scattered when you realize the chaos that surrounds you.
  • Selective Perception amounts to picking out those stimuli that are most likely to be important and ignoring the others.

It should be remembered that it would be detrimental to the perceiver if important information is ignored

In simple words 

You tend to hear, see and believe what you want to hear, see and believe.


  • You see your friend as a warm, friendly, peaceful, and law-abiding person. The police have arrested your friend for allegedly killing someone. Would you believe that your friend was capable of such crime ??

certain conventions govern selective perception, and these are discussed with reference to:

  • External physical stimuli
  • Absolute and differential thresholds
  • The disposition of perceiver


 Certain types of external physical stimuli attract our attention, such as 

  • size

  • repetition

  • position

  • color

  • moving objects in a stationary                       


  • novelty

  • contrast


  • Notices and warnings 

–Dynamic warning

–Static warning

  • Illustrations

  • Cues

  • Financial data

  • clarity

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