Another way of assessing the impact of traits on leadership is through the concept of emotional intelligence. This concept emerged in the early 1990s.

Emotional intelligence (EI) refers to the ability to perceive, control, and evaluate emotions. Some researchers suggest that emotional intelligence can be learned and strengthened, while other claim it is an inborn characteristic.

Since 1990, Peter Salovey and John D. Mayer have been the leading researchers on emotional intelligence. In their influential article "Emotional Intelligence," they defined emotional intelligence as, "the subset of social intelligence that involves the ability to monitor one's own and others' feelings and emotions, to discriminate among them and to use this information to guide one's thinking and actions" (1990).

Salovey and Mayer proposed a model that identified four different factors of emotional intelligence:

• the perception of emotion,
• the ability reason using emotions,
• the ability to understand emotion, and
• the ability to manage emotions.

According to Salovey and Mayer, the four branches of their model are, "arranged from more basic psychological processes to higher, more psychologically integrated processes. For example, the lowest level branch concerns the (relatively) simple abilities of perceiving and expressing emotion. In contrast, the highest level branch concerns the conscious, reflective regulation of emotion" (1997) (About.com).

Emotional intelligence appears to be an important component for leadership. It is believed that people who are more sensitive to their emotions and the impact of their emotions on others will be more effective leaders (Northouse, 2007, p.23).