BU Today

Science & Tech

The Power of Love

MED expert on the chemical magic behind Valentine’s Day

Michael Holick, MED chief of endocrinology, metabolism, and nutrition, says love is 50 percent chemical and 50 percent emotional.

When Michael Holick says love is in the air, he’s not kidding around. Holick, a professor and chief of endocrinology, metabolism, and nutrition at Boston University’s School of Medicine, believes that the first and most powerful force behind love is pheromones, chemicals secreted by both men and women that travel through the air. What the chemicals say to our unwary brains, essentially, is “check me out.” And in most cases, says Holick, we do just that.

To help readers make the most of Valentine’s Day and to better understand the age-old mystery of love, BU Today sent a few provocative questions to Holick. How would you prefer to be asked out on a date?

BU Today: How much of love is based on true emotions and how much is chemical?

Michael Holick: I’d say that probably 50 percent of love is chemical and 50 percent is emotion.

Which comes first, the emotional empathy or the effect of the chemicals?

I have a feeling that the chemical part comes first, although we are not aware of it at the time. Pheromones are very subtle but are extremely potent.

How powerful are they?

Good question. It’s hard to say, but I have a feeling that it’s just like moths, that we can send a signal for miles. We humans don’t fully appreciate our ability to detect minute quantities of pheromones. You could be 10 blocks away and not know what’s going on, but your brain may pick it up.

Does each of us walk around all day long sending out chemical signals that we are unaware of? 

There is no question about that. We are not aware of it, but chemicals very much influence our behavior. I’ll give you an example. It is well documented that if you put young women in the same dorm room, they all begin to cycle together. That’s one of the things that happens because of pheromones.

What is the evolutionary advantage of having all females ovulate at the same time?

Another good question. It may be that if you live at a time and in a society where there are few males around, you have a better chance of attracting a mate. It could also be that if all females ovulate at the same time, all offspring are born at the same time, and if you live in a time of predatory activity, the more young there are, the greater the chance of survival.

If people are turned on by pheromones that are floating in the air, why are they not attracted to many people? Why is intense sexual attraction usually aimed at one person?

Pheromones are one of the precipitating reasons that people become interested in each other. After that there are lots of visual signals that take place. Also, pheromones are only part of the chemical influence in love. Endorphins are also involved. When there is an intimate relationship, there is an increase in the production of endorphins, and that gives us what is called a greater satisfaction level, or general happiness. It’s a lot like a runner’s high.

How long does the high last?

It lasts as long as intimacy lasts, although it’s unclear what exactly happens after menopause. Prior to that the hormones are very high all the time.

When do we start discriminating and focus our desire on one person?

That’s where the visual signals come in. There are visual signals that attract us to one person, not all people. It may be something like the imprinting that occurs when a baby is born. There may be a secreted chemical signal that imprints on the male brain. This is highly speculative.

Are there other chemicals in nature that have a similar effect?

We know the aroma of certain foods can have an impact. With females, for instance, chocolate is a very significant part of their arousal in terms of their interest in eating something. That’s interesting because we know that chocolate has a lot of volatile chemicals that are released spontaneously in the atmosphere. You can smell chocolate. There is something acting very much like pheromones.

What about other stimuli? In other words, are there stimuli that people can put to good use to keep a romance going?

I’m sure there are a lot of different inputs that you can have, just touching or caressing different parts of the body that are not in any way sexual organs can have a huge impact. Certain sounds, too, can have a similar effect. Music can do it. There are all kinds of stimuli that can affect the central nervous system and alter beta endorphin levels and the production of pheromones.

How can we know what they are?

Many are imprinted from good experiences. Food certainly does that. Much of the stimuli is based on what we experience at certain times. The best thing you can do is learn what your significant other wants and desires. You have to know what arouses your partner and what will encourage your partner to remain your partner.

Art Jahnke can be reached at jahnke@bu.edu.