When you drop a male rat into a cage with a receptive female rat, you see an initial frenzy of copulation. Then, progressively, the male tires of that particular female. Even without an apparent change in her receptivity he reaches a point where he has little libido-and simply ignores her.
However, if you replace the original female with a fresh one, the male immediately revives and begins copulating again. You can repeat this process with fresh females until the rat nearly dies of exhaustion. The rat's renewed vigor does not reflect an increase in his wellbeing - although it will look (and temporarily feel to him) that way. His vigor comes from surges of a neurochemical called dopamine, which flood the reward circuitry of his primitive brain... so that he gets the job done.
In short, animals do not choose their mates randomly. They identify and reject those with whom they have already had sex. Scientists know this reflex as the "Coolidge Effect." It earned its name many years ago when President Coolidge and his wife were touring a farm. While the President was elsewhere, the farmer proudly showed Mrs. Coolidge a rooster that "could copulate with hens all day long, day after day." Mrs. Coolidge coyly suggested that the farmer tell that to Mr. Coolidge, which he did. The President thought for a moment and then inquired, "With the same hen?"
"No, sir," replied the farmer.
"Tell that to Mrs. Coolidge," retorted the President.
The Coolidge Effect has been observed in all mammals that have been tested. Scientists have observed it in females too. Female rodents, for example, flirt a lot more - arching in inviting displays - with unfamiliar partners than with those with which they've already copulated.
What's behind the Coolidge Effect? And is there a way around it? We've talked about a post-passion hangover that pushes partners apart. Here's a brief summary:
The hangover is the product of perfectly natural neurochemical shifts, which occur in the primitive part of the brain, or limbic system. This limbic system is the center of emotions, drives, impulses, and subconscious decision-making. Within the limbic system is the reward circuitry, which dopamine activates to urge us to take actions that further our survival or pass on our genes, such as eating, sex, bonding with offspring, taking risks.
Think of dopamine as the neurochemical of all motivation. You don't actually crave ice cream, or a winning lotto ticket, or a romp in the sack. You crave dopamine. In reality that blast of dopamine is your reward.
All addictive substances and activities increase dopamine. It's why they are addictive. (Is orgasm addictive? Yes, it has even been compared to shooting heroin in brain scans.) But addictive substances and activities don't give lasting pleasure. As soon as dopamine successfully motivates a behavior, it drops off, awaiting its next opportunity to push you around. One trigger for the Coolidge Effect is novelty itself.1 2
Another trigger is a drop in dopamine following orgasm. Instead of that delicious sense of aliveness and thrilling anticipation you felt when your dopamine was high, you now feel flat, or even needy or depleted. The orgasms themselves initiate this drop in dopamine. While dopamine is low, you are especially susceptible to anything at all that will raise your dopamine again, such as calorie-rich food, gambling, alcohol, a shopping spree, cocaine, porn on the internet, or sex. (See Sex and Addiction for more on this topic.) A new potential sex partner is one of the most effective "cures" for the "dopamine blues." As comedian Chris Rock crudely put it, "There's nothing like new [nooky] to clear the mind!" His reaction is just what biology intends.
While you are seeking to feel better, biology is striving to increase the genetic variety of your offspring. Genetic variety ensures that more of your offspring will survive changing conditions to pass on genes. A brand new partner briefly raises your dopamine more than sex with a familiar partner, however loving. Yet, despite this passing thrill, you don't actually increase your overall wellbeing by following biology's script. You'd be better off in a close, committed relationship. (More on that in a moment.)
The point is that biology's strategy is not truly a cure for your uncomfortable post-orgasm let down. Chris' head won't stay clear - and his primary partner may just hit it with a frying pan when she finds the condoms he left in his pocket. The Coolidge Effect reflex is strictly a temporary fix that will likely leave you feeling even more depleted. Your new partner will not satisfy you any more than your previous one.
Like a spinning wheel in a rodent's cage, the Coolidge Effect leads us in dizzying circles that do not improve our wellbeing - only our genes' chances. A man from LA, who had stopped counting at 350 sex partners, once mentioned that he was genuinely puzzled why he had lost interest (sexually) in each of them so quickly. The Coolidge Effect is the answer to his perplexity. Glen Wilson described its usual trajectory in The Science of Sex:
Before marriage it is usual for men to initiate intercourse at a fairly high frequency with their fiancée. After a few years of marriage, however, the husband's sexual appetite begins to wane and an apparent reversal of libido may even occur, with the now frustrated wife demanding more lovemaking than her 'tired' husband is able to supply. He, of course, is still perfectly capable of being aroused by his mistresses and office girls and, if fortunate enough to secure an invitation to an orgy, would have little difficulty completing intercourse with two or three anonymous young women in the course the evening's festivities. Sex therapists see many men who are reported as 'impotent' by their wives, but who privately confess to considerable prowess with a succession of mistresses.
Why do we fall for the same trick over and over? Because we assume that the intensity of our (dopamine-driven) anticipation equals the value to us of the behavior it's urging us to engage in. We are accustomed to relying on this subconscious dopamine reward mechanism to make sound decisions in many areas of our lives. When it comes to sex, however, this inner gauge misleads us. Evolutionary biology prizes quantity of offspring above quality of life. It doesn't care what makes us harmonious, happiest or healthiest. As a result, our ancient ancestors who impulsively had sex, lost interest, and wandered after their next partner were likely to pass on their genes…and their lovemaking habits.
However, humans are pair-bonders, unlike 95% of mammal species. This means we are designed to benefit from long-term companionship. The Coolidge Effect pushes us in the opposite direction. We're designed for tension between these two programs - our mating and our bonding programs - but it's up to us how we resolve that tension.
Another reason the dopamine reward system fails us is that it's set to react to the short-term repercussions of certain choices. For example, it's geared to give you a buzz when you select high calorie, sweet fare. This preference may have served your ancestors in selecting among the foods on the plains of Africa. However, it doesn't serve you in a culture where high-calorie, sugar-laden food is over abundant and made even more enticing by advertising geared to stimulate the reward circuit of your brain.
Similarly, your reward system doesn't take into account the full repercussions of sex. It gives you a buzz for pursuing fertilization opportunities, especially with new partners (even two-dimensional ones), without adjusting for how you will feel afterward, or how those feelings of depletion may damage your relationship - when you project them onto your partner. You won't even suspect what is at work when you later perceive your partner as needy and over-controlling, or selfish and insensitive.
This mechanism may also disregard the value of a committed relationship entirely in the interest of propelling your genes onward. It asks no small sacrifice in return for its offer of possible genetic immortality.
According to Dr. Dean Ornish in Love & Survival, love and intimacy are more powerful determinants of health than stopping smoking, more exercise, genetic make-up, improved diet, or prescription drugs. Trusted companionship has been shown to speed recovery, lower rates of illness, and increase longevity. Clearly, you would be better off working toward lasting harmony with a partner than pursuing a roller coaster ride of thrills and heartaches.
The best protection against the Coolidge Effect may be to learn to make love without the fertilization-driven sex that leaves you so susceptible to its siren song. If the ancients could do it, we can too. (For more on the Coolidge Effect see What If She Were Always In the Mood?)