The metaphor of a ticking biological clock is often used to refer to a woman’s growing urge to conceive before her childbearing years are over.

Now, two Florida State University researchers have discovered that there’s more truth to the phrase than one might think: The sound of a ticking clock can affect reproductive timing attitudes and lead some women to want to start a family at an earlier age.

Psychology graduate student Justin H. Moss and former Florida State professor Jon K. Maner completed two experiments to test the influence of a subtle environmental factor — the ticking of a small white kitchen timer — on people’s attitudes about reproductive timing.They outlined their findings in a paper, “The Clock Is Ticking: The Sound of a Ticking Clock Speeds Up Women’s Attitudes on Reproductive Timing,” published in the Springer journal Human Nature.

“The very subtle sound of a ticking clock changed the timing with which women sought to have children and the traits they sought in potential partners — both central aspects of women’s mating-related psychology,” Moss said.

In the first experiment, 59 men and women were asked questions about the age at which they’d like to marry and start a family. The experiment assessed whether the presence of a small kitchen timer would lead people of various childhood socioeconomic backgrounds to want to have children sooner or press the snooze button on their biological clocks.

In the second experiment, the researchers examined the extent to which 74 participants would alter the characteristics they sought in potential mates in order to have children sooner.

Their findings suggest that priming the idea of the passage of time through the sound of a ticking clock can influence various aspects of women’s reproductive timing. The effect was especially noticeable among women with lower childhood socioeconomic status. They wanted to get married and have their first child at a younger age than women with more resources. They also lowered the priority that they placed on men’s social status and long-term earning potential.

However, the effect of the clock was not the same for men — a result that was not surprising to the researchers, who noted that the reproductive lives of men are not as limited because they are able to father children well into old age.

Reproductive timing refers to the time frame and the specific years during which people begin to focus their energy and resources towards bearing and caring for their offspring.

The findings support previous research that suggests reproductive timing is greatly influenced by a person’s childhood years, his or her socioeconomic background and other subtle environmental factors.

“The ticking clock serves as a reminder that women’s reproductive potential is limited,” Moss said. “The study also illustrates that the way people respond to reproductive threat in adulthood is calibrated by their socioeconomic experiences in childhood.”

The findings are important for another reason, Maner said.

“Although most people like to think that personal decisions are a matter of their own free will, sometimes they are instead influenced by a person’s unconscious mind,” Maner said. “Very subtle things going on around us can affect very personal decisions — like when to have children — without us even realizing it.”