If your little finger reaches above a certain knuckle, you are supposedly outgoing. If it falls below, you are sensitive or private. The categories vary from post to post—which is already a warning that the finger is not measuring a stable personality construct.
Finger measurements produce weak, inconsistent personality links
Scientific work on finger length usually examines ratios such as 2D:4D—the relative length of the index and ring fingers—not a viral pinky-to-knuckle classification. A large study that also measured Big Five personality traits found only weak and inconsistent relationships between finger measures and personality.
Other studies have reported small correlations with selected psychological traits, but small population-level associations do not create a useful personality test for an individual.
Three leaps happen at once
Anatomy → category
A continuous physical measurement gets forced into a few neat groups.
Category → personality
A physical difference is assigned broad character descriptions without validation.
Personality → destiny
The quiz then predicts relationships, career or hidden talents from the same unsupported rule.