than it used to be 50 years ago.

These days, for most people, premarital sex is okay,

oral sex is okay.

In this post-"50 Shades of Grey" era, even kinky sex is okay.

But we're still very conflicted as a society and as individuals

over whether it's acceptable and healthy to have casual sex;

sex outside the confines of long-term, romantic relationships.

We are constantly surrounded by it,

yet we are often told it's bad for us, we shouldn't be doing it.

By the time we are 25, 70% of us will have hooked up at least once,

and yet most of us will worry we shouldn't really be doing it.

But there's something that doesn't make sense here to me

about this love-hate relationship we have with casual sex.

We all seem to agree that sex with a romantic partner

has all these amazing benefits,

from longer and healthier lives,

to better relationships and greater happiness.

So, how come that same sexual activity

has the exact opposite effect

if our partner is a stranger or a friend?

Is sex somehow good for us

only because of the love and commitment we feel for our partners?

And without that love and commitment,

it automatically turns into a destructive force?

Isn't there something good in just, you know, sex?

When I started my PhD in Developmental Psychology,

I decided to get to the bottom of this.

Is casual sex objectively bad for us?

Or is this just another grossly over-exaggerated moral sex panic

that the US has had no shortage of?

In the 10 years since, we've learned a great deal

about casual sex from social science research

- my own and that of other scholars -

but virtually 90% of that knowledge is based on US undergrads.

And trust me, you are not the only people hooking up.

(Laughter)

So to supplement our knowledge and understanding of this phenomenon,

I started this website, called "The Casual Sex Project."

It's an online space for people of all demographic backgrounds

to share their true stories of hook ups.

My hope was to give people a chance to tell their stories,

make sense of their experiences through this process of storytelling,

but also, to paint a more diverse, richer picture

of what casual sex really looks like;

what it means to people, what it feels like, what its aftermath may be.

In the 10 months since the website's been up,

it's been viewed over six million times.

Over 1200 stories have been shared by people from all over the world,

and it's been written about on six continents.

So what have all these stories and studies taught us about casual sex and well-being?

Well, here are a few things that you may not have been aware of.

First of all, casual sex has many potential benefits.

Perhaps the most obvious one is sexual pleasure.

Orgasms, hedonic ecstasy, if you will.

Then there are things like learning new sexual skills,

making new friends,

(Laughter)

it's a good one.

An increased sense of self-confidence,

accomplishment, desirability,

empowerment, freedom.

Then there are collecting fun stories and memories

to tell your friends at the senior citizens' home, many years later,

or share on the casual sex project.

There's even experiencing that deep, emotional,

spiritual, intellectual connection with another human being

that sometimes happens even though no romantic feelings are involved.

But casual sex has yet another powerful pull on us.

As Esther Perel so eloquently puts it,

humans have this fundamental need for adventure,

novelty, mystery, risk, danger,

the unknown, the unexpected.

Some more than others, but it's there in our DNA.

And that is a need that casual sex satisfies effortlessly

by its very nature,

and it's a need that's much more difficult, if not impossible, to meet

in the long-term part of long-term relationships.

Now, there are of course risks:

unsatisfying sex, broken hearts,

ruined friendships, regret, coercion,

confusion, awkwardness,

STI's and unwanted pregnancies,

social stigma, disrespectful partners.

Now, people fear that most of the time these cons outweigh the pros.

But that is simply not true.

Study after study finds this pattern

for how people feel following their hook ups.

For both men and women alike, positive post-hook-up reactions

- happy, pleased, excited -

are much stronger than negative hook up reactions;

used, empty, disappointed.

Other studies show that casual sex has little to no impact

on longer-term psychological well-being.

Things like self-esteem, life satisfaction, depression, anxiety.

Now, of course, this doesn't mean that all hook ups follow this pattern,

or that this pattern is typical of everybody who hooks up,

and that no one's well-being is ever affected.

No, these are just averages.

When you look more closely at the people and the experiences

making up these averages,

you find that some hook ups do indeed have the potential

to harm or benefit well-being.

And some people are more susceptible to that potential.

So whether casual sex is good for you or not

depends on who you are and how you do it.

There are many factors this relationship can depend on,

and I couldn't possibly cover all of them in one 18 minute talk.

But one critical one is "authenticity."

Doing only the kinds of things that are fully in line with who you are;

your beliefs, your values, your desires, your needs.

Casual sex is not for everyone.

Nothing sexual ever is, really.

Due to differences in nature, nurture, and life circumstances,

some of us have a much stronger general need for sexual novelty,

and much greater comfort having sex with people we don't know very well.

So figure out where you are on this spectrum.

Is hooking up with people you're not dating

something that sounds enjoyable, exciting,

an important experience to have?

Morally acceptable to you?

Would you be hooking up with this person

even if you are never going to see them afterwards?

If the answer to most of these is "no," you shouldn't really be doing it.

Now, there's a bit of an elephant in the room

when we talk about pleasure in heterosexual casual sex:

the orgasm gap between men and women.

In a study of over 20,000 undergrads,

80% of men had an orgasm during their most recent hook up.

(Laughter)

This was true of only 40% of women.

Now, there's an orgasm gap in romantic encounters too,

but it's twice as large in hook ups.

This doesn't mean that women aren't enjoying it necessarily.

In this same study, 90% of the women said they enjoyed their hook up very much,

or at least somewhat.

Most of them enjoyed it very much, about 70+%.

But we can all do better.

(Laughter)

I mean, this gap needs closing.

Women need to learn to be more selfish, demand their sexual pleasure.

And men need to learn to be more giving, try harder to please their partners,

even in the briefest of one night stands.

You know, casual sex doesn't have to be devoid of all intimacy and passion.

It's not like you're doing laundry or picking up your mail.

Try to give and get as much sexual pleasure out of every hook up.

That's the whole point.

One major factor that keeps people from engaging in casual sex to begin with

is the social stigma attached to it.

This dreaded reputation

is unfortunately much more constraining of women's behavior than it is of men's.

But here's an interesting thing.

People do indeed say

they don't want to be friends or spouses with promiscuous others.

But more promiscuous college students of both sexes actually report

having more friends and feeling less lonely

than their less promiscuous peers.

So, if casual sex is going to be a part of your life,

yes, there will be people who will judge you.

But you can surround yourself with people who won't.

Now, an unfortunate reality of hook ups, especially college hook ups,

is how often they are driven by alcohol.

When researchers asked freshmen women

to track all their sexual encounters over one academic year,

this is what they found.

The less known the partner was, the more likely alcohol was involved.

You can't see it unfortunately at the end over there,

but when it was a stranger, 90% of all hook ups involved drinking.

63% involved heavy drinking, four or more drinks.

Then you may look at this and be like, "Yeah, so what?"

But it's not, "So what."

This is really unfortunate.

Because judgment impaired due to alcohol or drugs

is the number one reason for unwanted hook ups,

hook ups you regret the next day.

A couple of drinks to set the mood or for liquid courage is one thing,

But getting smashed?

That makes you do things you didn't want to do

with people you didn't want to do them with,

it diminishes your physiological ability to enjoy sex or perform sexually,

it inhibits your psychological ability to set boundaries and express desires,

it weakens your determination to use condoms,

it makes you more sexually aggressive or more vulnerable to sexual aggression,

and it also just blurs your memories,

and I mean, don't you want to remember it?

If you need to be drunk to be hooking up, you should not be hooking up at all.

Now, sexual desire and romantic love

are two distinct psychological and physiological systems

that evolved for two different evolutionary purposes:

making babies versus staying together long enough for those babies to survive.

But the two systems are not independent.

Sex can set in motion a cascade of neurochemical processes in the brain

that lead to love.

Neurotransmitters released during sex

- oxytocin, vasopressin, dopamine -

they make you bond to your partner even if you didn't want that to happen.

And the more you have sex with that person,

the stronger that bond grows.

Then, when those bonds get broken, as they often do in casual relationships,

it hurts.

Now, some people are luckier;

their brains are wired in a way that they don't get attached very easily.

But you can also fight this involuntary infatuation with reason.

Not every person who gives you great orgasms and treats you well afterwards

would make a great long-term partner.

You know, go down your relationship checklist

and find all those red flags of incompatibility.

Then, resist the urge to text them 20 times a day,

(Laughter)

or start naming your kids and planning your life together

as soon as they leave your house.

Keep yourself busy.

Have a rotation of partners, perhaps.

Works for you all.

(Laughter)

Finally, casual sex is not just for single people.

Remember that novelty and adventure thing I talked about in the beginning?

Well, many people in long-term relationships also crave novelty,

sometimes much more so than single people.

Some try to suppress those needs and hope they go away;

others cheat and hope their partners don't find out.

But an increasing number of people, about 4-5% at our current best estimate,

are starting to incorporate casual sex

into their long-term, loving, committed relationships

in an open and honest way,

in a consensually, non-monogamous way.

If this is something that might interest you,

there is a growing movement of ethical or responsible non-monogamy out there

that you might want to explore,

starting with this awesome book called "The Ethical Slut."

All said and done,

there's nothing inherently wrong or inherently unhealthy

about wanting casual sex or having it often.