When most people read a book, newspaper, or magazine, they see the words as black marks on the page.

When most people read a book, newspaper, or magazine, they see the words as black marks on the page. This is not surprising given that ink in most publications is black. However, there is a group of people who do not see the words in front of them as black. Instead they might say that the number 4 is blue or the word gift is green. Others might say that the pain from a headache is orange, the flavor of sugar round, or a sniff of a bouquet of roses pink. What's going on here? According to neuroscientists, these people have a condition called synesthesia. The word synesthesia comes from the Greek words syn (meaning together) and aesthesis (meaning perception) and means "joined perception. " All humans have five senses-touch, vision, hearing, taste, and smell-and typically these are clearly separated from one another. However, for a person with synesthesia the boundaries between the senses are weak. So one sense, for example, sound, may seep across to another sense such as sight, so that the sound of an orchestra playing might be seen as green wobbly lines. This combination-an auditory stimulation accompanied by a visual sensation-is the most common type of synesthesia. Any simultaneous combination of two or more senses is considered a form of synesthesia. Neurologist Richard Cytowic became interested in this phenomenon after he found out his neighbor tasted shapes. Cytowic was convinced he should take a deeper look when less than two weeks later he encountered a colleague who saw the sound of his hospital pager as red lightning bolts. Cytowic and other scientists believe that synesthesia is not an abnormality. In fact, we all may experience synesthesia at birth. It is only when our brain develops that the boundaries between each of our senses become more refined. People with synesthesia, on the other hand, retain these indistinct boundaries throughout their lives. Another finding is that the relationships between the different sensory perceptions are consistent over time. Someone who hears the buzz of a bee as purple will always see it as purple. The sensations are also unique to individuals. One person may see the word table as yellow and another see it as green. Although anyone can create links between the senses and other ideas or objects through the use of metaphor (for example, heated debate, bubbly personality, or loud shirt), this is not the same as synesthesia. Synesthetes experience these relationships spontaneously without any conscious thought. One young synesthete blogger reports how disillusioned she felt when she saw a famous singer for the first time and he didn't match up to the color she had seen for him when she first heard him sing. Another reports how the sound of paper makes him feel physically sick, so he hates going to restaurants with paper tablecloths and napkins. Thus, while some negative reactions may result from synesthesia, Professor Simon Baron Cohen believes it is more useful to think of it as enriched perception, because synesthetes often use their condition as a means to enhance memory or as a source of inspiration. The prominent Russian artist Wassily Kandinsky's synesthesia may have triggered the creation of his famous portrayals of musical compositions as abstract paintings. Medical science has known about synesthesia for several centuries, but this revival of interest has increased our understanding. We now know that it is more frequent among women and lefthanders and that it appears to run in families. However, estimates of the number of people with synesthesia still vary widely, from 1 in 200 to 1 in 2, 000. This may be because many people who have the condition may not realize that it has a name.