"As we age, and become closer and more comfortable with one another, it could be that we are more able to express ourselves to each other. In other words, its possible that negativity is a normal aspect of close relationships that include a great deal of daily contact," said Kira Birditt, a research fellow at the University of Michigan Institute for

Social Research (ISR).

According to the research at the University of Michigan while our relationships with children and best friends tend to become less negative as we age, we are more likely to see our spouses as irritating and demanding.

However, "viewing our spouses more negatively over time may not be all bad. In fact, it might even be, well, positive," said Birditt.

The researcher said the increases in negativity over time may be indicative of learned patterns of interaction which have been reinforced and tend to persist over time.

"Interestingly, as relationships with spouses become more negative, relationships with children and friends appear to become less demanding and irritating over time," the research fellow stressed.