Introduction to Psychology/Sensation and Perception
Sensation and perception are related but different concepts. Sensation is the input about the physical world that is produced by our sensory receptors. Perception is the process by which the mind selects, organizes, and interprets sensations. Our eyes see, our ears hear, our hands touch--or do they? Without interpretation, there is no point to sensation.
How many senses are there? 
If you asked the person on the street how many senses there were, it is almost certain that you would hear "Five: sight, sound, taste, smell, and touch." This is the classical concept of human senses. However, researchers have identified two more:
- Kinesthesia, which is the sense of position of the parts of the body
- Vestibular senses, which detect gravity, linear acceleration, rotary acceleration, and overall provide balance
Taste and smell are related, and both use receptors located in the mouth and other tissues that line other cavities.
The sense of touch is actually a group of subsenses, which could be better-called the somatic senses (somatic means "body"). These subsenses include:
- Mechanoreception, which is the perception of pressure or vibration on the skin
- Thermoreception, which is the perception of heat
- Nociception, which is the perception of pain
Sensory receptors 
Sensory receptors are cells that are specialized for the task of transduction, or converting physical energy into neural impulses. There are many different types of sensory receptors, such as:
- Rods and cones in the retina, which transduce light.
- Cilla in the ear, which transduce sound
- Pressure, vibration, heat, and pain receptors in the skin
- Chemical receptors in the nasal cavities and mouth
- Muscle spindles
Gestalt Effect 
People have a tendency to see information and sensory images in tiny pieces. As pieces are sensed they form a larger pattern or picture.