[njchick]

Ones are unlikely to mistype themselves as Sevens, but Sevens occasionally mistype themselves as Ones. Sevens who have been under stress for prolonged periods of time may notice many average One behaviors, such as perfectionism and a need for order, and conclude that they must be Ones. While these traits may surface in certain extreme circumstances, a quick review of the Seven's life will usually reveal that rigid self-control, harsh inner criticism, and repression of impulses are not their dominant issues.
Another source of confusion is the shared idealism and sense of "mission" of the two types. Both types hold high ideals about the world and about human beings, but express these in markedly different ways. Sevens are usually very optimistic about the future and about things working out positively. Ones are far less so–they hold high standards and expect to be disappointed by people and by the world. Ones are fairly certain that they know their "mission" while for Sevens, it is more of a feeling. In Sevens, uncertainty about the nature of their mission creates a great deal of underlying anxiety. ("What if I miss my chance?") Sevens may also think they are Ones because they see themselves as "perfectionists," but their style of perfectionism is very different. Ones' perfectionism drives them to berate themselves for days because they misplaced a comma in an otherwise excellent one hundred-page report. Sevens' "perfectionism" may lead them to become frustrated because the sea food salad they ordered in a restaurant was not exactly the way they wanted it.
The two types are quite different in a number of other ways. Sevens are spontaneous and adventurous–they like to be free to change plans and to follow their inspiration. Ones get frustrated when plans are changed, and usually do not like to deviate from the careful preparations they have made. Sevens are usually unselfconscious socially, Ones are usually very self-conscious socially. Ones are methodical and sticklers for time-management and for following efficient procedures. Sevens have a more fluid sense of time, and balk at being "bogged down" by procedures. Sevens are curious and open-minded, but tend to get distracted and scattered. Ones are more focused and directed, but can be opinionated and closed-minded. Sevens are driven by anxiety: Ones by simmering anger, and so forth.