It turns out Harry was right when he told Sally that men and women can't be friends because "the sex part always gets in the way."

While it has long been known that feelings of attraction is very common between people in opposite-sex friendships, the latest findings show that such feelings make these friendships more of a burden than a benefit.

In a new study, researchers asked participants to list the advantages and disadvantages of having opposite-sex friends.  Of all the participants, 32 percent listed feelings of attraction as a cost, while only 6 percent listed these feelings as a benefit.

However, women were more likely to report feelings of attraction as a disadvantage compared to men, with 47 percent of women between the ages of 18 and 23 listing attraction as a cost in an opposite-sex friendship and 22 percent of men reporting the same. The results of the study showed that opposite-sex friendships may also harm romantic relationships, with 38 percent of women and 25 percent of men between the ages 27 and 50 reporting that jealousy from their romantic partners was a disadvantage of maintain an opposite-sex friendship.

In fact researchers from the University of Wisconsin-Eau Claire found that the more attraction people felt in an opposite-sex relationship, the less satisfied they were with their current romantic relationship. "Our findings implicate attraction in cross-sex friendship as both common and of potential negative consequence for individuals' long-term mateships," the study authors wrote in the study published in the Journal of Social and Personal Relationships.

In another experiment, involving 88 college-age men and women who came into the laboratory with an opposite-sex friend, participants were asked to rate their level of attraction toward their friend on a scale of one to nine.

Results from the study showed that men, whether attached or single, were slightly more likely to be attracted to their female friends and would more likely want to go on a date with them than the other way around. Researchers found that men also assumed that their female friends were more romantically interested in them than they actually were and that women tended to be unaware of this fact.

While single and attached women showed about the same level of attraction to their male friend, attached women tended to only want something to come out of that attraction if there was trouble in their current relationship.

Scientists postulated that interacting with a member of the opposite sex instinctually initiates mating strategies that evolved tens of thousands of years ago.