In his search for a match for Yitzchak, Eliezar set up the following test:

"Let the maiden to whom I shall say, 'Please tip over your jug so I may drink' and who replies, 'drink, and I will even water your camels', her will You have designated for Your servant, for Yitzchak; and I may know through her that you have done kindness with my master." Ch.24/14

Eliezer was obviously looking for the trait of chesed (kindness) in his search for the perfect match. He would ask for just himself, and she would offer water for his camels, as well. However, the Beis HaLevi explains that he was also testing her intelligence. For once she has given him to drink from her jug, what is she to do with the remaining water? To use that water for her family would be out of the question, because as a stranger she should be concerned about his germs. So what should she do? To take it all the way home and then spill it out would be a waste of energy. To spill it out in front of him would be insulting. Therefore, the most intelligent decision would be to give it to his camels; a conservation of energy, water and human dignity!

Another girl, though of equal intelligence, could have come to a different decision. For example, a selfish girl could have opted to take it all the way home to spill it, just to avoid doing something nice for someone else. Or, if she were insensitive, it wouldn't bother her to spill it out in front of him. So the fact that Rivka did choose to give the leftovers to his camels shows that she possessed both intelligence and kindness.