Want to increase your sex appeal? It's as easy as being nice, according to leading psychologist Associate Professor Gery Karantzas of the Deakin School of Psychology.

"It doesn't matter what countries in the world or cultures you look at, by and large, the number one characteristic people look for in a potential partner is warmth and trustworthiness," said Dr Karantzas, reports news.com.au.

"Physical attractiveness kind of matters but we don't put anywhere near the emphasis that people think we do. Warmth and trustworthiness kills off everything else," he said.

"This idea that women are after a broody guy is garbage - no one wants to be treated badly in a relationship. Bottom line is for us to survive and feel valued as individuals we need people to care for us and we have a desire for human connection and affection.

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"And if you give people a trade-off where they can choose between a very good looking but cold person and someone who is less good-looking but very warm and loving, people always pick the friendly person," he said.

The theory even extends to our celebrity crushes.

An online survey by dating company eHarmony asked a representative sample of 1000 Australians to nominate the celebrity they would most like to spend the night with.

For women, Chris Hemsworth and Channing Tatum topped the list.

For men, it was Margot Robbie, followed by Delta Goodrem and Jennifer Lawrence - who tied in equal second place.

Sexologist Dr Nikki Goldstein believes the appeal of Hemsworth and Tatum lies in their family values and public commitment to their partners.

"Aussie women are over the bad boy," said Dr Goldstein. "We like a cheeky guy but we also like someone who's got a down-to-earth caring side and with Channing, he's always talking about his wife.

"He seems like a good partner, a good father and a good person. And he rocked the dad-bod for a while, so that makes him seem like a normal guy."

We want someone we can have fun with, but who will there to tuck the kids into bed after bath time.

Similarly celebrities such as Robbie, Goodrem and Lawrence, who are all known for their down-to-earth attitudes and bubbly dispositions also fit the bill of individuals deemed more attractive for their friendliness.

"Men always look for big smiles and kind eyes," explained neuropsychotherapist Dr Trisha Stratford, best known the match-matching expert on TV show, Married at First Sight.

"Women like a masculine face, a strong jaw and a definite brow. What that jaw and face shape relates to is a primal instinct that tells women, "this man is going to protect and support me." said Dr Stratford.

To help educate Australians on the science of attraction and relationships, Dr Karantzas launched Karantzas relationshipscienceonline.com this week.