Psychological effects of having a sister on National Sister's Day

The benefits our sisters bring to our lives are limitless. But having a sister has less obvious effects on psychological behavior.

In honor of National Sister's Day, read on for five ways in which your sister is affecting your life you might not have guessed.

1. Households with sisters are better at communication

Sisters encourage more effective communication and collaboration within family units, according to a study co-authored by University of Ulster Professor Tony Cassidy. The same study found that brothers seemingly have the opposite effect - sorry boys!

2. Girls with sisters are more ambitious

Cassidy's research also found evidence for girls with sisters striving toward loftier goals than their counterparts who are not lucky enough to have a sister.

Sisters are remarkable role models for each other. Healthy competition can motivate greater success for both of them, so long as they remain supportive and avoid jealousy.

Speaking of sibling rivalry…

3. Women with older sisters are more competitive… While men with older sisters are less competitive.

The competitive nature fostered between sisters spills over into other aspects of their lives, according to research conducted by economist Hiroko Okudaira and her colleagues.

But perhaps men with sisters learn to be more protective rather than competitive, as a study involving Japanese high school and college students theorized that men who have sisters are less competitive in general.

Men with sisters stand out in more ways than one.

4. Men with sisters are better at talking to women

Studies suggest that men with sisters are better at making small talk with members of the opposite sex.

When men were paired with women for five to 15 minute conversations, those who grew up with sisters were more well-liked than those men who did not, according to the results of University of Texas psychologist William Ickes' study.

He study found men with older sisters engaged in more natural conversation and more easily kept the conversation going. Practice makes perfect!

5. People with sisters have better mental health

Brigham Young University Professor Laura Padilla-Walker found that having a sister - no matter the age - decreased adolescents' levels of loneliness, self-consciousness, and fear.

It's not surprising that a sister's love fights against depression and improves her siblings' mental well-being.

We have plenty of reasons to celebrate our sisters. On National Sister's Day and every day, it is important to remind them of how much they are loved.