The researchers wrote "Given the positive association of signature size and sociable dominance, larger signatures could be interpreted as a signal of the inclination to stand out and occupy a central position within a group."
For the study, which was published in the Journal of Research in Personality, psychologists analysed the handwritten signatures of 340 men and women along with their answers to several personality questionnaires.
They analysed the results in a way that controlled for the effects of other factors, such as the number of characters in their name and their overall writing style. The results showed that, while both men and women with florid signatures like being the centre of attention, only women scored highly when it came to vanity.
The researchers, from the University of the Republic in Uruguay, suggested that this is because narcissism is expressed differently in men and women.
Previous research, they explained, has found narcissistic men tend to express the trait through lack of empathy, while narcissistic women are more likely to express it "through extreme concern with physical appearance, of which handwritten signatures could be an expression".
Similarly, a separate study found that women - but not men - who embellished their signature with exclamation marks and underlining also scored higher on narcissism.