Human Memory
Memory is the next part of our model of the user as an information processing system. There are generally three types of memory: sensory memory, short-term memory and long-term memory.


Sensory memory
The sensory memories act as buffers for stimuli received through the senses. A sensory memory exists for each sensory channel: iconic memory for visual stimuli, echoic memory for aural stimuli and haptic memory for touch. Information is passed from sensory memory into short-term memory by attention, thereby filtering the stimuli to only those which are of interest at a given time.

Short-term memory
Short-term memory acts as a scratch-pad for temporary recall of the information under process. For instance, in order to understand this sentence you need to hold in your mind the beginning of the sentence you read the rest. Short term memory decays rapidly (200 ms.) and also has a limited capacity. Chunking of information can lead to an increase in the short term memory capacity. Thst is the reason why a hyphenated phone number is easier to rememeber than a single long number. The successful formation of a chunk is known as closure. Interference often causes disturbance in short-term memory retention. This accounts for the desire to complete the tasks held in short term memory as soon as possible.

Long-term memory
Long-term memory is intended for storage of information over a long time. Information from the working memory is transferred to it after a few seconds. Unlike in working memory, there is little decay.

What is a headache?
A Headache is defined as a pain in the head or upper neck. It is one of the most common locations of pain in the body and has many causes.

How are headaches classified?
Headaches have numerous causes, and in 2007 the International Headache Society agreed upon an updated classification system for headache. Because so many people suffer from headaches and because treatment sometimes is difficult, it is hoped that the new classification system will allow health care practitioners come to a specific diagnosis as to the type of headache and to provide better and more effective treatment.

There are three major categories of headaches:
1. primary headaches,
2. secondary headaches, and
3. cranial neuralgias, facial pain, and other headaches

What are primary headaches?
Primary headaches include migraine, tension, and cluster headaches, as well as a variety of other less common types of headache.

Tension headaches are the most common type of primary headache. Up to 90% of adults have had or will have tension headaches. Tension headaches occur more commonly among women than men.

Migraine headaches are the second most common type of primary headache. An estimated 28 million people in the United States (about 12% of the population) will experience a migraine headache. Migraine headaches affect children as well as adults. Before puberty, boys and girls are affected equally by migraine headaches, but after puberty, more women than men are affected. It is estimated that 6% of men and up to 18% of women will experience a migraine headache in their lifetime.