Twenty years after concluding men are from Mars and women are from Venus, John Gray says we're no better at communicating with our lovers, and confidence in marriage is at its lowest ebb.
Among the factors contributing to the now parlous state of marriage, Dr Gray says, are the changing roles of men and women and the fact that most big cities are in the grip of a man drought.
The other challenge for the shrinking number of couples who do take the plunge is the outdated role models for successful partnerships, he says.
"As human beings we learn so much from watching our parents," he says.
"(But) their behavioural skills, their values, their communication tools are completely outdated and they're not sufficient for couples to deal with relationship problems today."
He cites the example of a 1950s businessman who would return home after a long day to be greeted by his cinch-waisted Betty Draper-style wife with a glass of scotch and freshly cooked dinner.
"But that's not going to happen today," he says.
Dr Gray believes that culture existed to support women, whose primary motivation for marriage was financial security, and men, who as the breadwinners, needed time to relax after a hard day's work.
"Today, we don't have a culture yet to define male and female roles in relationships," he says, adding that it leaves each unsure of their role.
"For hundreds of years we have had certain dance steps for a relationship to the music we'd had for 100 years. That music has changed."
Women's rise to relative equality has meant marriage is no longer a financial imperative.
"Women are more financially self-sufficient; the priority of finding a man to depend upon becomes lessened."
Figures from the Australian Bureau of Statistics show fewer people are indeed walking down the aisle and those who do choose to are waiting until their late 20s (27 for women and 29 for men).
The rate of marriage in Australia has dropped from 0.7 per cent in 1989 to 0.5 per cent in 2009. Divorce rates reached an all-time low in 2008, but the numbers began to climb again in 2009.
Relationships Australia spokeswoman Lyn Fletcher disagrees with Dr Gray about declining confidence in marriage, preferring to think people are simply expressing their decisions to make a long-term commitment in different ways.
A couple's decision to eschew bridesmaids and matching bath towels doesn't mean the wholesale rejection of long-term commitment, she says.
The modern couple is instead buying houses, signing mortgages, having children and - sometimes but not always - getting married.
She believes flexibility is the hallmark of the modern relationship and that pliability extends to how the relationship is defined. She doesn't like the division of gender.
"Fundamentally, people are looking for companionship. They're looking for a sense of commitment to make a relationship work, and for closeness and intimacy," she says.
Ms Fletcher agrees with Dr Gray that men's and women's roles in society and, by extension, the family unit have changed. But unlike the American psychologist, she says there has been momentous progress over the past 20 years in how people manage those changes.
The rise of the career woman in the late 1980s meant women started to demand their partners take a more active role in the home and with the family.
"Women were trying to do it all and so they were expecting more from their men," says Fletcher, adding that men began to rethink their role, in particular what it meant to be a father and a partner, not just provider.
"Around that time it became a relationship of real equals because both partners were sharing the roles in order for there to be a sense of equality."
Twenty years on, Fletcher says, Australian couples are finding themselves in a situation where a dual income is no longer a luxury.
In a world where the housing market and government policy are putting pressure on couples to be dual-income, Fletcher says people are more likely to focus on career development and to expect more from life.
The result of this is that they can be unwilling to make sacrifices or compromises when it comes to looking for love.
This view is in line with Gray's second point of contention: the man drought, he says, is contributing to the change in gender roles as women are becoming the pursuers because they have fewer men to choose from.
"The amount of men that they have to pick from are generally less because, generally, women at a professional level are looking for professional men.
"Traditionally, women marry up, men marry down."
Gray and Fletcher agree this leaves the growing number of professional women in the unenviable position of having a smaller pool of suitable suitors to choose from.
Security alone is no longer enough to entice them into matrimony; they are looking for love and support that will help them cope with the stresses of balancing a work and home life, and they do not have much confidence in men to provide this.
"There is an evolutionary shift, a societal shift," Gray says.
Fletcher says aspirational men and women may be expecting too much. Men and women might need to stop looking for Mr or Ms Right, and realise Mr or Ms Good Enough should not be overlooked.
But she's quick to qualify that, saying it's not about putting people down or settling, but acknowledging that nobody is perfect and being open to work with someone to build a successful relationship.
"I think the more superficial things, the other characteristics, like their capacity to earn or their educational status are characteristics that make people attractive to us, but whether they're characteristics that make a relationship work long term is another matter," she says.
"If you'll only go out with a professional or a blonde, or someone slim, you're narrowing your field straight away.
"Yes, it's partly about your values and you can't have a total values clash, but just because someone's a professional, doesn't mean you're going to have the same values."
Though they're at odds on whether the institution of marriage is being assailed by modern life, Fletcher and Gray agree on one thing: To ensure a long and happy partnership, compromise and communication are vital.
nothing yet to be aded
ihave not yet ane personl relationship to any os thes let me know specifikly apout relation ships !