Nice and kind persons are often too passive in conflict situations or while negotiating salary. Women that adopted "manly behavior style" on their job ( alpha female ) are earning 5% more than other female colleagues that have usual female behavior pattern like openness, kindness and flexibility. ( Essex university study ).  

The study titled "Does it worth to be kind?" organized by employment institute from Nurnberg has shown that female employees that are aggressive, diligent and persistent are earning 5% more than their colleagues that are passive and sloppy. The research has shown that male candidates that are kind are earning less. The research covered five thousand men and women between 20 and 60. the scope of research was test that was assessing five traits: openness, conscientious, extroversion, adjustability and neurotic behavior.

Alpha Female A dominant or assertive woman, a woman boss, the leader among a group of females. Previously referred to the hierarchy among animals, now used to type human beings.

The research has shown that women that are tense and have changing mood, on average are earning 3% less their female counterparts. At the same time men with neurotic behavior does not have lower salary than usual. Those men that are kind and are earning less.
 

Women that are embracing challenges are earning 5% more than female colleague that does not like challenges, while their extroversion does not affect their income. The research has shown that beside intelligence all personal traits are affecting their salary.  

Still, way of behavior on the job does not reflect the real nature always. Some people tend to adjust their attitude toward working environment. For example, it is frequently considered that female employees are usually paid less, since they are lacking ambitiousness that men more often have. But the lack of the ambitiousness on the job does not necessary mean that somebody can not have more ambitious performance. Ambitiousness is often leading to promotions, but to more obligation and less private time too. Therefore some employees, are choosing less challenging job, in order to dedicate more time to private life and family.